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Sample records for magnetic dipole excitations

  1. 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.

  2. 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.

  3. Lossless propagation of magnetic dipole excitations on chains of dielectric particles with high refractive index

    NASA Astrophysics Data System (ADS)

    Zhuromskyy, O.; Peschel, U.

    2014-09-01

    Lossless propagation of longitudinal magnetic dipole waves along chains of high-index subwavelength particles is predicted for a narrow frequency range around the magnetic Mie resonance of the individual particles. Mathematical analogies between dipole and magnetoinductive waves are used to reduce back-reflections thus improving the power transfer efficiency of respective particle waveguides. The proposed technique can be used to optimize the propagation of even more complex particle-based configurations.

  4. 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.

  5. Microscopic description of ground state magnetic moment and low-lying magnetic dipole excitations in heavy odd-mass 181Ta nucleus

    NASA Astrophysics Data System (ADS)

    Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar

    2016-07-01

    The ground state magnetic moments and the low-lying magnetic dipole (Ml) transitions from the ground to excited states in heavy deformed odd-mass 181Ta have been microscopically investigated on the basis of the quasiparticle-phonon nuclear model (QPNM). The problem of the spurious state mixing in M1 excitations is overcome by a restoration method allowing a self-consistent determination of the separable effective restoration forces. Due to the self-consistency of the method, these effective forces contain no arbitrary parameters. The results of calculations are compared with the available experimental data, the agreement being reasonably satisfactory.

  6. Derivation of magnetic fields on a metal cylinder excited by longitudinal and transverse magnetic dipole transmitters: I. Cylinder in unbounded dissipative dielectric medium

    NASA Astrophysics Data System (ADS)

    Freedman, Robert

    2015-09-01

    We derive new and exact analytical and convergent integral representations for the frequency-dependent complex magnetic fields Hz(a, ϕ, z) and Hϕ(a, ϕ, z) excited by oscillating point magnetic dipole transmitters on the surface of an infinitely long metal cylinder of radius a in an unbounded dissipative dielectric medium. Hz(a, ϕ, z) is calculated for a longitudinally oriented magnetic dipole parallel to the cylinder axis and Hϕ(a, ϕ, z) for a transversely oriented magnetic dipole perpendicular to the axis. The solutions are relevant to the computation of phase shifts and attenuations measured by electromagnetic propagation logging tools, which have oscillating longitudinal and transverse magnetic dipole transmitters either on a metal drill collar or on a cylindrical antenna pad. The integral representations can be readily evaluated using simple numerical integration algorithms, e.g., Simpson's rule, to accurately compute the complex magnetic fields on the cylinder surface. A second paper will address the two-layer cylindrical media problem.

  7. Selective Excitation of Terahertz Magnetic and Electric Dipoles in Er3 + Ions by Femtosecond Laser Pulses in ErFeO3

    NASA Astrophysics Data System (ADS)

    Mikhaylovskiy, R. V.; Huisman, T. J.; Pisarev, R. V.; Rasing, Th.; Kimel, A. V.

    2017-01-01

    We show that femtosecond laser pulse excitation of the orthoferrite ErFeO3 triggers pico- and subpicosecond dynamics of magnetic and electric dipoles associated with the low energy electronic states of the Er3 + ions. These dynamics are readily revealed by using polarization sensitive terahertz emission spectroscopy. It is shown that by changing the polarization of the femtosecond laser pulse one can excite either electric dipole-active or magnetic dipole-active transitions between the Kramers doublets of the 15/2I4 ground state of the Er3 + (4 f11 ) ions. These observations serve as a proof of principle of polarization-selective control of both electric and magnetic degrees of freedom at terahertz frequencies, opening up new vistas for optical manipulation of magnetoelectric materials.

  8. Derivation of the magnetic field on a metal cylinder excited by a longitudinal magnetic dipole transmitter: II. Cylinder in a two-layer dissipative dielectric medium

    NASA Astrophysics Data System (ADS)

    Freedman, Robert

    2016-11-01

    We derive an exact convergent analytical solution for the complex frequency-dependent magnetic field on the surface of an infinitely long and perfectly conducting metal cylinder situated in a cylindrically layered dissipative medium. The inhomogeneous medium consists of two exterior cylindrical layers that are concentric with the cylinder. The magnetic field on the cylinder is excited by a longitudinally oriented oscillating magnetic dipole transmitter on the cylinder surface. An exact analytical solution to this problem has not been previously published and is of theoretical as well as practical importance, e.g., in modeling the responses of electromagnetic wave propagation well logging tools. It is shown that the magnetic field on the cylinder surface can be expressed as a real-axis integral; however, the integrand oscillates rapidly and diverges for large values of the integration variable. The real-axis integral is replaced by the sum of two convergent branch line integrals and a sum over the residues of the complex poles in the integrand of the real-axis integral. The poles correspond physically to waveguide modes that propagate with discrete wave numbers. A pole search algorithm is developed to locate the positions of the poles and compute their residues. Phase shifts and attenuations of the magnetic field between receivers for a 1.1 GHz well logging tool are computed to elucidate the pole spectra and the relative contributions of the waveguide modes and the branch cut integrals for different thicknesses of the innermost dielectric layer and for different layer properties.

  9. 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.

  10. 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…

  11. Magnetic dipole oscillations and radiation damping

    NASA Astrophysics Data System (ADS)

    Stump, Daniel R.; Pollack, Gerald L.

    1997-01-01

    We consider the problem of radiation damping for a magnetic dipole oscillating in a magnetic field. An equation for the radiation reaction torque is derived, and the damping of the oscillations is described. Also discussed are runaway solutions for a rotating magnetic dipole moving under the influence of the reaction torque, with no external torque.

  12. Magnetic dipole interactions in crystals

    DOE PAGES

    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

  13. 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

  14. Magnetic dipole interactions in crystals

    SciTech Connect

    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, 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

  15. 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…

  16. Magnetic dipole moments for composite dark matter

    SciTech Connect

    Aranda, Alfredo; Barajas, Luis; Cembranos, Jose A.R. E-mail: luisedua@buffalo.edu

    2016-03-01

    We study neutral dark matter candidates with a nonzero magnetic dipole moment. We assume that they are composite states of new fermions related to the strong phase of a new gauge interaction. In particular, invoking a dark flavor symmetry, we analyze the composition structure of viable candidates depending on the assignations of hypercharge and the multiplets associated to the fundamental constituents of the extended sector. We determine the magnetic dipole moments for the neutral composite states in terms of their constituents masses.

  17. Spin waves and magnetic excitations

    SciTech Connect

    Borovik-Romanov, A.S.; Sinha, S.K.

    1988-01-01

    This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.

  18. Conductor Development for High Field Dipole Magnets

    SciTech Connect

    Scanlan, R.M.; Dietderich, D.R.; Higley, H.C.

    2000-03-01

    Historically, improvements in dipole magnet performance have been paced by improvements in the superconductor available for use in these magnets. The critical conductor performance parameters for dipole magnets include current density, piece length, effective filament size, and cost. Each of these parameters is important for efficient, cost effective dipoles, with critical current density being perhaps the most important. Several promising magnet designs for the next hadron collider or a muon collider require fields of 12 T or higber, i.e. beyond the reach of NbTi. The conductor options include Nb{sub 3}Sn, Nb{sub 3}Al, or the high temperature superconductors. Although these conductors have the potential to provide the combination of performance and cost required, none of them have been developed sufficiently at this point to satisfy all the requirements. This paper will review the status of each class of advanced conductor and discuss the remaining problems that require solutions before these new conductors can be considered as practical. In particular, the plans for a new program to develop Nb{sub 3}Sn and Nb{sub 3}Al conductors for high energy physics applications will be presented. Also, the development of a multikiloamp Bi-2212 cable for dipole magnet applications will be reported.

  19. Near-Field Magnetic Dipole Moment Analysis

    NASA Technical Reports Server (NTRS)

    Harris, Patrick K.

    2003-01-01

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

  20. Magnetic dipole strength in 128Xe and 134Xe in the spin-flip resonance region

    NASA Astrophysics Data System (ADS)

    Massarczyk, R.; Rusev, G.; Schwengner, R.; Dönau, F.; Bhatia, C.; Gooden, M. Â. E.; Kelley, J. Â. H.; Tonchev, A. Â. P.; Tornow, W.

    2014-11-01

    The magnetic dipole strength in the energy region of the spin-flip resonance is investigated in 128Xe and 134Xe using quasimonoenergetic and linearly polarized γ -ray beams at the High-Intensity γ -Ray Source facility in Durham, North Carolina, USA. Absorption cross sections were deduced for the magnetic and electric and dipole strength distributions separately for various intervals of excitation energy, including the strength of states in the unresolved quasicontinuum. The magnetic dipole strength distributions show structures resembling a resonance in the spin-flip region around an excitation energy of 8 MeV. The electric dipole strength distributions obtained from the present experiments are in agreement with the ones deduced from an earlier experiment using broad-band bremsstrahlung instead of a quasimonoenergetic beam. The experimental magnetic and electric dipole strength distributions are compared with phenomenological approximations and with predictions of a quasiparticle random phase approximation in a deformed basis.

  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. 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.

  3. 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.

  4. Excited state dipole moments of 4-(dimethylamino)benzaldehyde

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2007-11-01

    The effect of various polar solvents on the location of absorption and dual fluorescence (short wavelength emission, SE, and long wavelength emission, LE) of 4-(dimethylamino)benzaldehyde (DMABA) at room temperature was investigated. It was found that the fluorescence intensities ratio LE/SE is constant for concentrations ranging from 10 -5 M to 10 -1 M, which evidences that the LE-band is not of excimer origin. Based on the batochromic shift of electronic spectra of DMABA and Bilot-Kawski theory the values of excited state dipole moments in SE: μeSE=7.6D and the Onsager radius a = 4.3 Å were found using the known from literature value of ground state dipole moment μg = 5.6 D. For the emitting twisted intramolecular charge transfer (TICT) excited state the value of μeLE=12D was found.

  5. 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.

  6. Spin waves in rings of classical magnetic dipoles

    NASA Astrophysics Data System (ADS)

    Schmidt, Heinz-Jürgen; Schröder, Christian; Luban, Marshall

    2017-03-01

    We theoretically and numerically investigate spin waves that occur in systems of classical magnetic dipoles that are arranged at the vertices of a regular polygon and interact solely via their magnetic fields. There are certain limiting cases that can be analyzed in detail. One case is that of spin waves as infinitesimal excitations from the system’s ground state, where the dispersion relation can be determined analytically. The frequencies of these infinitesimal spin waves are compared with the peaks of the Fourier transform of the thermal expectation value of the autocorrelation function calculated by Monte Carlo simulations. In the special case of vanishing wave number an exact solution of the equations of motion is possible describing synchronized oscillations with finite amplitudes. Finally, the limiting case of a dipole chain with N\\longrightarrow ∞ is investigated and completely solved.

  7. 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.

  8. Magnetic field decay in model SSC dipoles

    SciTech Connect

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

    1988-08-01

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

  9. SSC collider dipole magnets field angle data

    SciTech Connect

    Kuchnir, M.; Bleadon, M.; Schmidt, E.; Bossert, R.; Carson, J.; Delchamps, S.W.; Gourlay, S.; Hanft, R.; Koska, W.; Lamm, M.J.; Mazur, P.O.; Orris, D.; Ozelis, J.; Strait, J.; Wake, M. ); DiMarco, J.; Devred, A.; Kuzminski, J.; Yu, Y.; Zheng, H. ); Ogitsu, T. (Superconducting Super Collider

    1992-09-01

    In the fabrication of both 40 and 50 mm collider dipole superconducting magnets, surveys of the direction of the magnetic field along their length have been taken. This data besides being used for certifying compliance with the specifications for the finished magnet, yields interesting information on the straightness and rigidity of the coil placement between some stages in their manufacture and testing. A discussion on the measuring equipment and procedures is given. All of the 40 mm magnets that were built or cryostat at Fermilab have at least one of these surveys, and a summary of the data on them is presented. Most of the 50 mm magnets built and cold tested at Fermilab have been surveyed before and after insertion in the cryostat and before and after being cold tested. A summary of this data is also presented.

  10. Excitation-energy dependence of the giant dipole resonance width

    NASA Astrophysics Data System (ADS)

    Enders, G.; Berg, F. D.; Hagel, K.; Kühn, W.; Metag, V.; Novotny, R.; Pfeiffer, M.; Schwalb, O.; Charity, R. J.; Gobbi, A.; Freifelder, R.; Henning, W.; Hildenbrand, K. D.; Holzmann, R.; Mayer, R. S.; Simon, R. S.; Wessels, J. P.; Casini, G.; Olmi, A.; Stefanini, A. A.

    1992-07-01

    High-energy γ rays have been measured in coincidence with heavy fragents in deeply inelastic reactions of 136Xe+48Ti at 18.5 MeV/nucleon. The giant dipole resonance (GDR) strength function is deduced from an analysis of the photon spectra within the statistical model. The GDR width Γ is studied as a function of the fragment excitation energy E*. A saturation at about Γ=10 MeV is observed for E*/A>=1.0 MeV/nucleon.

  11. 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.

  12. Electric dipole excitation of 208Pb by polarized electron impact

    NASA Astrophysics Data System (ADS)

    Jakubassa-Amundsen, D. H.; Ponomarev, V. Yu.

    2016-03-01

    The cross sections and spin asymmetries for the excitation of 1- states in 208Pb by transversely polarized electrons with collision energy of 30-180MeV have been examined within the DWBA scattering formalism. As examples, we have considered a low-lying 1- state and also states belonging to the pygmy dipole and giant dipole resonances. The structure of these states and their corresponding transition charge and current densities have been taken from an RPA calculation within the quasiparticle phonon model. The complex-plane rotation method has been applied to achieve the convergence of the radial DWBA integrals for backward scattering. We have studied the behaviour of the cross sections and spin asymmetries as a function of electron energy and scattering angle. The role of the longitudinal and transversal contributions to the excitation has been thoroughly studied. We conclude that the spin asymmetry S, related to unpolarized outgoing electrons, is mostly well below 1% even at the backward scattering angles and its measurement provides a challenge for future experiments with polarized electrons.

  13. 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.

  14. Simultaneous Measurement of the Three-Dimensional Orientation of Excitation and Emission Dipoles

    NASA Astrophysics Data System (ADS)

    Karedla, Narain; Stein, Simon C.; Hähnel, Dirk; Gregor, Ingo; Chizhik, Anna; Enderlein, Jörg

    2015-10-01

    The emission properties of most fluorescent emitters, such as dye molecules or solid-state color centers, can be well described by the model of an oscillating electric dipole. However, the orientations of their excitation and emission dipoles are, in most cases, not parallel. Although single molecule excitation and emission dipole orientation measurements have been performed in the past, no experimental method has so far looked at the three-dimensional excitation and emission dipole geometry of individual emitters simultaneously. We present the first experimental study, using defocused imaging in conjunction with radially polarized excitation scanning, to measure both the excitation as well as emission dipole orientations of single molecules, which allows us to sample the distribution of their mutual orientation. We find an unexpectedly broad distribution of the angle between both dipoles which we attribute to the interaction between the observed molecules and the substrate they are immobilized on.

  15. Helical dipole magnets for polarized protons in RHIC

    SciTech Connect

    Syphers, M.; Courant, E.; Fischer, W.

    1997-07-01

    Superconducting helical dipole magnets will be used in the Brookhaven Relativistic Heavy Ion Collider (RHIC) to maintain polarization of proton beams and to perform localized spin rotations at the two major experimental detector regions. Requirements for the helical dipole system are discussed, and magnet prototype work is reported.

  16. Nature of low-lying electric dipole resonance excitations in 74Ge

    NASA Astrophysics Data System (ADS)

    Negi, D.; Wiedeking, M.; Lanza, E. G.; Litvinova, E.; Vitturi, A.; Bark, R. A.; Bernstein, L. A.; Bleuel, D. L.; Bvumbi, S.; Bucher, T. D.; Daub, B. H.; Dinoko, T. S.; Easton, J. L.; Görgen, A.; Guttormsen, M.; Jones, P.; Kheswa, B. V.; Khumalo, N. A.; Larsen, A. C.; Lawrie, E. A.; Lawrie, J. J.; Majola, S. N. T.; Masiteng, L. P.; Nchodu, M. R.; Ndayishimye, J.; Newman, R. T.; Noncolela, S. P.; Orce, J. N.; Papka, P.; Pellegri, L.; Renstrøm, T.; Roux, D. G.; Schwengner, R.; Shirinda, O.; Siem, S.

    2016-08-01

    Isospin properties of dipole excitations in 74Ge are investigated using the (α ,α'γ ) reaction and compared to (γ ,γ' ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy, being populated by both isoscalar and isovector probes, and the other at high energy, excited only by the electromagnetic probe. Relativistic quasiparticle time blocking approximation (RQTBA) calculations show a reduction in the isoscalar E 1 strength with an increase in excitation energy, which is consistent with the measurement.

  17. 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.

  18. Velocity-dependent dipole forces on an excited atom

    NASA Astrophysics Data System (ADS)

    Donaire, M.; Lambrecht, A.

    2016-02-01

    We present a time-dependent calculation of the velocity-dependent forces which act on an excited atomic dipole in relative motion with respect to ground state atoms of a different kind. Both its interaction with a single atom and with a dilute atomic plate are evaluated. In either case, the total force consists of a conservative van der Waals component and a nonconservative Röntgen component. On physical grounds, the former corresponds to the velocity-dependent recoil experienced by the excited atom in the processes of absorption and emission of the photons that it exchanges with the ground-state atoms on a periodic basis. The latter corresponds to the time-variation of the Röntgen momentum, which is also mediated by the periodic exchange of quasiresonant photons. We find that, at leading order, all these interactions are linear in velocity. In the nonretarded regime the van der Waals force dominates, being antiparallel to the velocity. On the contrary, in the retarded regime the velocity-dependent forces oscillate in space, van der Waals and Röntgen forces are of the same order in the atom-atom interaction, and the Röntgen component dominates in the atom-surface interaction.

  19. 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.

  20. 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.

  1. 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.

  2. Lunar magnetic field - Permanent and induced dipole moments

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Coleman, P. J., Jr.; Schubert, G.

    1974-01-01

    Apollo 15 subsatellite magnetic field observations have been used to measure both the permanent and the induced lunar dipole moments. Although only an upper limit of 1.3 x 10 to the 18th gauss-cubic centimeters has been determined for the permanent dipole moment in the orbital plane, there is a significant induced dipole moment which opposes the applied field, indicating the existence of a weak lunar ionosphere.

  3. Need for remeasurements of nuclear magnetic dipole moments

    NASA Astrophysics Data System (ADS)

    Gustavsson, Martin G.; Mårtensson-Pendrill, Ann-Marie

    1998-11-01

    The need for a reassessment of nuclear magnetic dipole moments is prompted by recent experiments on the ground-state hyperfine structure in highly charged hydrogenlike systems which are sufficiently sensitive to probe QED effects. This work gives an overview of the magnetic dipole moments for the nuclei of interest, i.e., 165Ho, 185,187Re, 203,205Tl, 207Pb, and 209Bi. It is found that the present uncertainties in the nuclear magnetic dipole moment limit the interpretation of the accurate experimental hyperfine structures for these systems.

  4. Determination of ground and excited state dipole moments via electronic Stark spectroscopy: 5-methoxyindole.

    PubMed

    Wilke, Josefin; Wilke, Martin; Meerts, W Leo; Schmitt, Michael

    2016-01-28

    The dipole moments of the ground and lowest electronically excited singlet state of 5-methoxyindole have been determined by means of optical Stark spectroscopy in a molecular beam. The resulting spectra arise from a superposition of different field configurations, one with the static electric field almost parallel to the polarization of the exciting laser radiation, the other nearly perpendicular. Each field configuration leads to different intensities in the rovibronic spectrum. With an automated evolutionary algorithm approach, the spectra can be fit and the ratio of both field configurations can be determined. A simultaneous fit of two spectra with both field configurations improved the precision of the dipole moment determination by a factor of two. We find a reduction of the absolute dipole moment from 1.59(3) D to 1.14(6) D upon electronic excitation to the lowest electronically excited singlet state. At the same time, the dipole moment orientation rotates by 54(∘) showing the importance of the determination of the dipole moment components. The dipole moment in the electronic ground state can approximately be obtained from a vector addition of the indole and the methoxy group dipole moments. However, in the electronically excited state, vector addition completely fails to describe the observed dipole moment. Several reasons for this behavior are discussed.

  5. Propagation of magnetic dipole radiation through a medium.

    PubMed

    Arnoldus, Henk F; Xu, Zhangjin

    2016-05-01

    An oscillating magnetic dipole moment emits radiation. We assume that the dipole is embedded in a medium with relative permittivity ϵr and relative permeability μr, and we have studied the effects of the surrounding material on the flow lines of the emitted energy. For a linear dipole moment in free space the flow lines of energy are straight lines, coming out of the dipole. When located in a medium, these field lines curve toward the dipole axis, due to the imaginary part of μr. Some field lines end on the dipole axis, giving a nonradiating contribution to the energy flow. For a rotating dipole moment in free space, each field line of energy flow lies on a cone around the axis perpendicular to the plane of rotation of the dipole moment. The field line pattern is an optical vortex. When embedded in a material, the cone shape of the vortex becomes a funnel shape, and the windings are much less dense than for the pattern in free space. This is again due to the imaginary part of μr. When the real part of μr is negative, the field lines of the vortex swirl around the dipole axis opposite to the rotation direction of the dipole moment. For a near-single-negative medium, the spatial extent of the vortex becomes huge. We compare the results for the magnetic dipole to the case of an embedded electric dipole.

  6. 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.

  7. 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.

  8. Estimation of ground and excited state dipole moments of some laser dyes

    NASA Astrophysics Data System (ADS)

    Biradar, D. S.; Siddlingeshwar, B.; Hanagodimath, S. M.

    2008-03-01

    The ground state ( μg) and the excited state ( μe) dipole moments of three laser dyes namely 2, 5-diphenyl-1, 3, 4- oxadiazole (PPD), 2, 2″-dimethyl-p-terphenyl (DMT) and 1, 3-diphenyl benzene (MT) were studied at room temperature in various solvents. The ground state dipole moments ( μg) of all the three laser dyes were determined experimentally by Guggenheim method. The excited state dipole moments ( μe) were estimated from Lippert's, Bakshiev's and Chamma Viallet's equations by using the variation of the Stokes shift with the solvent dielectric constant and refractive index. Ground and excited state dipole moments were evaluated by means of solvatochromic shift method and also the excited state dipole moments are determined in combination with ground state dipole moments. It was observed that dipole moment values of excited states ( μe) were higher than corresponding ground state values ( μg), indicating a substantial redistribution of the π-electron densities in a more polar excited state for all the dyes investigated.

  9. 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

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

    PubMed

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

    2016-01-27

    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.

  11. Estimation of first excited singlet-state dipole moments of aminoanthraquinones by solvatochromic method.

    PubMed

    Siddlingeshwar, B; Hanagodimath, S M

    2009-04-01

    The ground state (micro(g)) and the excited state (micro(e)) dipole moments of three substituted anthraquinones, namely 1-aminoanthracene-9,10-dione (AAQ), 1-(methylamino)anthracence-9,10-dione (MAQ) and 1,5-diaminoanthracene-9,10-dione (DAQ) were estimated in various solvents. The dipole moments (micro(g) and micro(e)) were estimated from Lippert, Bakhshiev, Kawski-Chamma-Viallet, McRae and Suppan equations by using the variation of Stokes shift with the solvent dielectric constant and refractive index. The excited state dipole moments were also calculated by using the variation of Stokes shift with microscopic solvent polarity parameter (Epsilon(T)(N)). It was observed that dipole moment values of excited states (micro(e)) were higher than corresponding ground state values (micro(g)), indicating a substantial redistribution of the pi-electron densities in a more polar excited state for all the molecules investigated.

  12. Comments on the determination of excited state dipole moment of molecules using the method of solvatochromism.

    PubMed

    Kawski, A; Bojarski, P

    2011-11-01

    The present note comments on several publications which appeared in different journals containing many inaccurate statements and lacking honest citations of basic papers dealing with the application of solvatochromism to determine excited state dipole moments.

  13. Estimation of first excited singlet-state dipole moments of aminoanthraquinones by solvatochromic method

    NASA Astrophysics Data System (ADS)

    Siddlingeshwar, B.; Hanagodimath, S. M.

    2009-04-01

    The ground state ( μg) and the excited state ( μe) dipole moments of three substituted anthraquinones, namely 1-aminoanthracene-9,10-dione (AAQ), 1-(methylamino)anthracence-9,10-dione (MAQ) and 1,5-diaminoanthracene-9,10-dione (DAQ) were estimated in various solvents. The dipole moments ( μg and μe) were estimated from Lippert, Bakhshiev, Kawski-Chamma-Viallet, McRae and Suppan equations by using the variation of Stokes shift with the solvent dielectric constant and refractive index. The excited state dipole moments were also calculated by using the variation of Stokes shift with microscopic solvent polarity parameter ( ETN). It was observed that dipole moment values of excited states ( μe) were higher than corresponding ground state values ( μg), indicating a substantial redistribution of the π-electron densities in a more polar excited state for all the molecules investigated.

  14. Ground and excited state dipole moments of coumarin 337 laser dye

    NASA Astrophysics Data System (ADS)

    Raikar, U. S.; Tangod, V. B.; Mannopantar, S. R.; Mastiholi, B. M.

    2010-11-01

    This paper reports that the effects of spectral properties of coumarin 337 laser dye have been investigated in different solvents considering solvent parameters like dielectric constant ( є) and refractive index ( n) of different solvent polarities. The ground state ( μg) and excited state ( μe) dipole moments are calculated using Lippert's, Bakhshiev's, and Kawski-Chamma-Viallet's equations. In all these three equations the variation of Stokes shift was used to calculate the excited state ( μe) dipole moment. It is observed that the Bakhshiev method is comparatively better than the other two methods for ground state and excited state dipole moment calculations. The angle between the excited state and ground state dipole moments is also calculated.

  15. 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.

  16. 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.

  17. All-dielectric hollow nanodisk for tailoring magnetic dipole emission.

    PubMed

    Feng, Tianhua; Xu, Yi; Liang, Zixian; Zhang, Wei

    2016-11-01

    We propose a silicon hollow nanodisk for enhancing magnetic dipole (MD) emission. The Purcell factor can be more than 300, which is one order of magnitude larger than the silicon nanosphere case. It is demonstrated that the silicon hollow nanodisk resembles the function of an azimuthally polarized beam for tailoring the magnetic and electric dipole (ED) emission. It is shown that MD emission can be significantly enhanced, while ED emission will be suppressed when emitters are located in the hollow of the nanodisk. The dependence of the Purcell factor on the geometry parameters is also studied. Our results might facilitate the on-chip engineering of magnetic light emission.

  18. Multiple Magnetic Dipole Modeling Coupled with a Genetic Algorithm

    NASA Astrophysics Data System (ADS)

    Lientschnig, G.

    2012-05-01

    Magnetic field measurements of scientific spacecraft can be modelled successfully with the multiple magnetic dipole method. The existing GANEW software [1] uses a modified Gauss-Newton algorithm to find good magnetic dipole models. However, this deterministic approach relies on suitable guesses of the initial parameters which require a lot of expertise and time-consuming interaction of the user. Here, the use of probabilistic methods employing genetic algorithms is put forward. Stochastic methods like these are well- suited for providing good initial starting points for GANEW. Furthermore a computer software is reported upon that was successfully tested and used for a Cluster II satellite.

  19. 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.

  20. Longitudinal Gradient Dipole Magnet Prototype for APS at ANL

    SciTech Connect

    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.; Kerby, J. S.; Makarov, A. V.

    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 rotational coils, a stretched wire, and a Hall probe. Measurement results are discussed and compared with simulations.

  1. Longitudinal Gradient Dipole Magnet Prototype for APS at ANL

    DOE PAGES

    Kashikhin, V. S.; Borland, M.; Chlachidze, G.; ...

    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

  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. Late kinetic decoupling of light magnetic dipole dark matter

    SciTech Connect

    Gondolo, Paolo; Kadota, Kenji

    2016-06-07

    We study the kinetic decoupling of light (≲10 GeV) magnetic dipole dark matter (DM). We find that present bounds from collider, direct DM searches, and structure formation allow magnetic dipole DM to remain in thermal equilibrium with the early universe plasma until as late as the electron-positron annihilation epoch. This late kinetic decoupling leads to a minimal mass for the earliest dark protohalos of thousands of solar masses, in contrast to the conventional weak scale DM scenario where they are of order 10{sup −6} solar masses.

  4. Dipole polarizability, sum rules, mean excitation energies, and long-range dispersion coefficients for buckminsterfullerene C 60

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Thakkar, Ajit J.

    2011-11-01

    Experimental photoabsorption cross-sections combined with constraints provided by the Kuhn-Reiche-Thomas sum rule and the high-energy behavior of the dipole-oscillator-strength density are used to construct dipole oscillator strength distributions for buckminsterfullerene (C60). The distributions are used to predict dipole sum rules Sk, mean excitation energies Ik, the frequency dependent polarizability, and C6 coefficients for the long-range dipole-dipole interactions of C60 with a variety of atoms and molecules.

  5. Isospin properties of electric dipole excitations in 48Ca

    NASA Astrophysics Data System (ADS)

    Derya, V.; Savran, D.; Endres, J.; Harakeh, M. N.; Hergert, H.; Kelley, J. H.; Papakonstantinou, P.; Pietralla, N.; Ponomarev, V. Yu.; Roth, R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Wörtche, H. J.; Zilges, A.

    2014-03-01

    Two different experimental approaches were combined to study the electric dipole strength in the doubly-magic nucleus 48Ca below the neutron threshold. Real-photon scattering experiments using bremsstrahlung up to 9.9 MeV and nearly mono-energetic linearly polarized photons with energies between 6.6 and 9.51 MeV provided strength distribution and parities, and an (α,α‧γ) experiment at Eα=136 MeV gave cross sections for an isoscalar probe. The unexpected difference observed in the dipole response is compared to calculations using the first-order random-phase approximation and points to an energy-dependent isospin character. A strong isoscalar state at 7.6 MeV was identified for the first time supporting a recent theoretical prediction.

  6. Bistability between equatorial and axial dipoles during magnetic field reversals.

    PubMed

    Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel

    2012-06-08

    Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.

  7. 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.

  8. Measurement of AC electrical characteristics of SSC superconducting dipole magnets

    SciTech Connect

    Smedley, K M; Shafer, R E

    1992-01-01

    Experiments were conducted to measure the AC electrical characteristics of SSC superconducting dipole magnets over the frequency range of 0.1 Hz to 10 kHz. A magnet equivalent circuit representing the magnet DC inductance, eddy current losses, coil-to-ground and turn-to-turn capacitance, was synthesized from the experimental data. This magnet equivalent circuit can be used to predict the current ripple distribution along the superconducting magnet string and can provide dynamic information for the design of the collider current regulation loop.

  9. Dipole Excitation of Soft and Giant Resonances in 132Sn and neighboring unstable nuclei

    NASA Astrophysics Data System (ADS)

    Boretzky, Konstanze

    2006-04-01

    The evolution of dipole-strength distributions above the one-neutron threshold was investigated for exotic neutron-rich nuclei in a series of experiments using the electromagnetic projectile excitation at beam energies around 500 MeV/u. For halo nuclei, the large observed dipole strength (shown here for 11Be) is explained within the direct-breakup model to be of non-collective character. For neutron-rich oxygen isotopes, the origin of the observed low-lying strength is concluded to be due to single-particle transitions on theoretical grounds. The dipole strength spectra for 130,132Sn exhibit resonance-like structures observed at energies around 10 MeV exhausting a few percent of the Thomas-Reiche-Kuhn (TRK) sum rule, separated clearly from the dominant Giant Dipole Resonance (GDR). The data agree with predictions for a new dipole mode related to the oscillation of excess neutrons versus the core nucleons ("pygmy resonance").

  10. Self-generated magnetic dipoles in weakly magnetized beam-plasma system.

    PubMed

    Jia, Qing; Mima, Kunioki; Cai, Hong-bo; Taguchi, Toshihiro; Nagatomo, Hideo; He, X T

    2015-02-01

    A self-generation mechanism of magnetic dipoles and the anomalous energy dissipation of fast electrons in a magnetized beam-plasma system are presented. Based on two-dimensional particle-in-cell simulations, it is found that the magnetic dipoles are self-organized and play important roles in the beam electron energy dissipation. These dipoles drift slowly in the direction of the return flow with a quasisteady velocity, which depends upon the magnetic amplitude of the dipole and the imposed external magnetic field. This dipole formation provides a mechanism for the anomalous energy dissipation of a relativistic electron beam, which would play an important role in collisionless shock and ion shock acceleration.

  11. The permanent and induced magnetic dipole moment of the moon

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Coleman, P. J., Jr.; Lichtenstein, B. R.; Schubert, G.

    1974-01-01

    Magnetic field observations with the Apollo 15 subsatellite have been used to deduce the components of both the permanent and induced lunar dipole moments in the orbital plane. The present permanent lunar magnetic dipole moment in the orbital plane is less than 1.3 times ten to the eighteenth power gauss-cu cm. Any uniformly magnetized near surface layer is therefore constrained to have a thickness-magnetization product less than 2.5 emu-cm per g. The induced moment opposes the external field, implying the existence of a substantial lunar ionosphere with a permeability between 0.63 and 0.85. Combining this with recent measures of the ratio of the relative field strength at the ALSEP and Explorer 35 magnetometers indicates that the global lunar permeability relative to the plasma in the geomagnetic tail lobes is between 1.008 and 1.03.

  12. Test results from Fermilab 1.5 m model SSC collider dipole magnets

    SciTech Connect

    Koska, W.; Bossert, R.; Carson, J.; Coulter, K.J.; Delchamps, S.; Gourlay, S.; Jaffery, T.S.; Kinney, W.; Lamm, M.J.; Ozelis, J.P.; Strait, J.; Wake, M.

    1991-09-01

    We will present results from tests of 1.5 m model SSC collider dipole magnets. These R&D magnets are identical to the 15 m full length dipoles currently being assembled at Fermilab in all important aspects except length. Because of their small size they can be built faster and tested more extensively than the long magnets. The model magnets are used to optimize design parameters for, and to indicate the performance which can be expected from, the 15 m magnets. The are instrumented with voltage taps over the first two current blocks for quench localization and with several arrays of strain gauge transducers for the study of mechanical behavior. The stress at the poles of the inner and outer coils is monitored during construction and, along with end force and shell strain, during excitation. Magnetic measurements are made several times during each magnet`s lifetime, including at operating temperature and field. We will report on studies of the quench performance, mechanical behavior and magnetic field of these magnets.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

    Córsico, A. H.; Althaus, L. G.; Miller Bertolami, M. M.; Kepler, S. O.; García-Berro, E.

    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 (μν) 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 (Pi dot) 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 Pi dot 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 μν lesssim 10-11 μB. 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.

  15. Retraining of the 1232 Main Dipole Magnets in the LHC

    SciTech Connect

    Verweij, A.; Auchmann, B.; Bednarek, M.; Bottura, L.; Charifoulline, Z.; Feher, S.; Hagen, P.; Modena, M.; Le Naour, S.; Romera, I.; Siemko, A.; Steckert, J.; Tock, J. Ph; Todesco, E.; Willering, G.; Wollmann, D.

    2016-01-05

    The Large Hadron Collider (LHC) contains eight main dipole circuits, each of them with 154 dipole magnets powered in series. These 15-m-long magnets are wound from Nb-Ti superconducting Rutherford cables, and have active quench detection triggering heaters to quickly force the transition of the coil to the normal conducting state in case of a quench, and hence reduce the hot spot temperature. During the reception tests in 2002-2007, all these magnets have been trained up to at least 12 kA, corresponding to a beam energy of 7.1 TeV. After installation in the accelerator, the circuits have been operated at reduced currents of up to 6.8 kA, from 2010 to 2013, corresponding to a beam energy of 4 TeV. After the first long shutdown of 2013-2014, the LHC runs at 6.5 TeV, requiring a dipole magnet current of 11.0 kA. A significant number of training quenches were needed to bring the 1232 magnets up to this current. In this paper, the circuit behavior in case of a quench is presented, as well as the quench training as compared to the initial training during the reception tests of the individual magnets.

  16. Supersolid phase in atomic gases with magnetic dipole interaction

    SciTech Connect

    Buehler, Adam; Buechler, Hans Peter

    2011-08-15

    A major obstacle for the experimental realization of a supersolid phase with cold atomic gases in an optical lattice is the weakness of the nearest-neighbor interactions achievable via magnetic dipole-dipole interactions. In this paper, we show that by using a large filling of atoms within each well, the characteristic energy scales are strongly enhanced. Within this regime, the system is well described by the rotor model, and the qualitative behavior of the phase diagram derives from mean-field theory. We find a stable supersolid phase for realistic parameters with chromium atoms.

  17. 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

  18. The Fermilab Main Injector Dipole construction techniques and prototype magnet measurements

    SciTech Connect

    Bleadon, M.E.; Brown, B.C.; Chester, N.S.; Desavouret, E.; Garvey, J.D.; Glass, H.D.; Harding, D.J.; Harfoush, F.A.; Holmes, S.D.; Humbert, J.C. )

    1992-01-01

    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. In this paper 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.

  19. 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.

  20. Electron Cloud Trapping in Recycler Combined Function Dipole Magnets

    SciTech Connect

    Antipov, Sergey A.; Nagaitsev, S.

    2016-10-04

    Electron cloud can lead to a fast instability in intense proton and positron beams in circular accelerators. In the Fermilab Recycler the electron cloud is confined within its combined function magnets. We show that the field of combined function magnets traps the electron cloud, present the results of analytical estimates of trapping, and compare them to numerical simulations of electron cloud formation. The electron cloud is located at the beam center and up to 1% of the particles can be trapped by the magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a Recycler combined function dipole this multiturn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The multi-turn build-up can be stopped by injection of a clearing bunch of 1010 p at any position in the ring.

  1. 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.

  2. 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.

  3. Revisiting the photophysical properties and excited singlet-state dipole moments of several coumarin derivatives.

    PubMed

    Cisse, Lamine; Djande, Abdoulaye; Capo-Chichi, Martine; Delatre, François; Saba, Adama; Tine, Alphonse; Aaron, Jean-Jacques

    2011-08-01

    The solvent effects on the electronic absorption and fluorescence emission spectra of several coumarins derivatives, containing amino, N,N-dimethyl-amino, N,N-diethyl-amino, hydroxyl, methyl, carboxyl, or halogen substituents at the positions 7, 4, or 3, were investigated in eight solvents with various polarities. The first excited singlet-state dipole moments of these coumarins were determined by various solvatochromic methods, using the theoretical ground-state dipole moments which were calculated by the AM1 method. The first excited singlet-state dipole moment values were obtained by the Bakhshiev, Kawski-Chamma-Viallet, Lippert-Mataga, and Reichardt-Dimroth equations, and were compared to the ground-state dipole moments. In all cases, the dipole moments were found to be higher in the excited singlet-state than in the ground state because of the different electron densities in both states. The red-shifts of the absorption and fluorescence emission bands, observed for most compounds upon increasing the solvent polarity, indicated that the electronic transitions were of π-π* nature.

  4. Revisiting the photophysical properties and excited singlet-state dipole moments of several coumarin derivatives

    NASA Astrophysics Data System (ADS)

    Cisse, Lamine; Djande, Abdoulaye; Capo-Chichi, Martine; Delatre, François; Saba, Adama; Tine, Alphonse; Aaron, Jean-Jacques

    2011-08-01

    The solvent effects on the electronic absorption and fluorescence emission spectra of several coumarins derivatives, containing amino, N,N-dimethyl-amino, N,N-diethyl-amino, hydroxyl, methyl, carboxyl, or halogen substituents at the positions 7, 4, or 3, were investigated in eight solvents with various polarities. The first excited singlet-state dipole moments of these coumarins were determined by various solvatochromic methods, using the theoretical ground-state dipole moments which were calculated by the AM1 method. The first excited singlet-state dipole moment values were obtained by the Bakhshiev, Kawski-Chamma-Viallet, Lippert-Mataga, and Reichardt-Dimroth equations, and were compared to the ground-state dipole moments. In all cases, the dipole moments were found to be higher in the excited singlet-state than in the ground state because of the different electron densities in both states. The red-shifts of the absorption and fluorescence emission bands, observed for most compounds upon increasing the solvent polarity, indicated that the electronic transitions were of π-π* nature.

  5. Cavity QED based on collective magnetic dipole coupling: spin ensembles as hybrid two-level systems.

    PubMed

    Imamoğlu, Atac

    2009-02-27

    We analyze the magnetic dipole coupling of an ensemble of spins to a superconducting microwave stripline structure, incorporating a Josephson junction based transmon qubit. We show that this system is described by an embedded Jaynes-Cummings model: in the strong coupling regime, collective spin-wave excitations of the ensemble of spins pick up the nonlinearity of the cavity mode, such that the two lowest eigenstates of the coupled spin wave-microwave cavity-Josephson junction system define a hybrid two-level system. The proposal described here enables new avenues for nonlinear optics using optical photons coupled to spin ensembles via Raman transitions. The possibility of strong coupling cavity QED with magnetic dipole transitions also opens up the possibility of extending quantum information processing protocols to spins in silicon or graphene, without the need for single-spin confinement.

  6. 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.

  7. Magnetic dipole moment determination by near-field analysis

    NASA Technical Reports Server (NTRS)

    Eichhorn, W. L.

    1972-01-01

    A method for determining the magnetic moment of a spacecraft from magnetic field data taken in a limited region of space close to the spacecraft. The spacecraft's magnetic field equations are derived from first principles. With measurements of this field restricted to certain points in space, the near-field equations for the spacecraft are derived. These equations are solved for the dipole moment by a least squares procedure. A method by which one can estimate the magnitude of the error in the calculations is also presented. This technique was thoroughly tested on a computer. The test program is described and evaluated, and partial results are presented.

  8. 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.

  9. Recent results on giant dipole resonance decays in highly excited nuclei

    SciTech Connect

    Snover, K.A.

    1991-01-01

    Some recent results on Giant Dipole Resonance (GDR) decays in highly excited, equilibrated nuclei, are discussed based primarily on work done at Seattle. Four sections address the following topics: oblate shapes of rotating, highly excited Zr--Mo nuclei; adiabatic versus motionally narrowed' GDR decay; large spin-driven deformations observed in hot medium-mass nuclei; and search for entrance channel effects in GDR decay following [sup 58]Ni [plus] [sup 92]Zr fusion. 22 refs.

  10. Recent results on giant dipole resonance decays in highly excited nuclei

    SciTech Connect

    Snover, K.A.

    1991-12-31

    Some recent results on Giant Dipole Resonance (GDR) decays in highly excited, equilibrated nuclei, are discussed based primarily on work done at Seattle. Four sections address the following topics: oblate shapes of rotating, highly excited Zr--Mo nuclei; adiabatic versus `motionally narrowed` GDR decay; large spin-driven deformations observed in hot medium-mass nuclei; and search for entrance channel effects in GDR decay following {sup 58}Ni {plus} {sup 92}Zr fusion. 22 refs.

  11. POLARIZATION OF MAGNETIC DIPOLE EMISSION AND SPINNING DUST EMISSION FROM MAGNETIC NANOPARTICLES

    SciTech Connect

    Hoang, Thiem; Lazarian, Alex

    2016-04-20

    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.

  12. Magnetic Shielding Studies for Electric Dipole Moment Experiments

    NASA Astrophysics Data System (ADS)

    Gould, Harvey; Feinberg, B.

    2014-09-01

    Electric dipole moment experiments are necessarily sensitive to magnetic fields and hence require effective magnetic shielding. In testing the shielding factor of single-layer Permalloy (Carpenter HyMu ``80'' ®) cylinders, we find time-dependent effects lasting tens of minutes to thousands of minutes when a static magnetic field is applied to a Permalloy cylinder that has been demagnetized in a region of near-zero field. A decrease in the magnetic field, measured at the center of the cylinder, of about 20 percent is observed for applied fields ranging from 0.5 A/m to 16 A/m. The latter applied field is comparable to the Earth's magnetic field. Effects that resemble these have been seen in other ferromagnetic materials.

  13. Exciting Reflectionless, Unidirectional Edge Mode in Bianisotropic Meta-waveguide Using Rotating Dipole Antenna

    NASA Astrophysics Data System (ADS)

    Xiao, Bo; Antonsen, Thomas; Ott, Edward; Anlage, Steven; Ma, Tzuhsuan; Shvets, Gennady

    Electronic chiral edge states in Quantum Hall Effect systems has attracted a lot of attention in recent years because of its unique directionality and robustness against scattering from disorder. Its electromagnetic counterpart can be found in photonic crystals, which is a material with periodic dielectric constant. Here we present the experimental results demonstrating the unidirectional edge mode inside a bi-anisotropic meta-waveguide (BMW) structure. It is a parallel plate waveguide with metal rods placed in a hexagonal lattice. Half of the rods are attached to the top plate while the other half are attached to the bottom plate creating a domain wall. The edge mode is excited by two loop antennas placed perpendicular to each other within one wavelength, generating a rotating magnetic dipole that couples to the left or right-going mode. The transmission measurement are taken along the BMW boundary and shows high transmission only around the edge, thus confirming the presence of an edge mode. We also demonstrated that very high directivity can be achieved when the input amplitude and phase of the two loop antennas are tuned properly This work is funded by the ONR under Grants No. N00014130474 and N000141512134, and the Center for Nanophysics and Advanced Materials (CNAM).

  14. Estimation of ground and excited state dipole moments of Oil Red O by solvatochromic shift methods

    NASA Astrophysics Data System (ADS)

    Sıdır, İsa; Gülseven Sıdır, Yadigar

    2015-01-01

    Absorption and fluorescence spectra of Oil Red O (abbreviated as ORO) are recorded in various solvents with different polarity in the range of 250-900 nm, at room temperature. The solvatochromic shift methods have been used to determine the ground state (μg) and excited state (μe) dipole moments depending on dielectric constant and refractive index functions. It is observed that fluorescence spectra show positive solvatochromism whereas absorption spectra do not indicates sensitive behavior to solvent polarity. Excited state dipole moment is found as higher than those of ground state for all of the used methods and it is attributed to more polar excited state of ORO. Theoretical μg has been determined by quantum chemical calculations using DFT and semi empirical methods. HOMO, LUMO, molecular electrostatic potential (MEP) and solvent accessible surface of ORO are calculated by using DFT-B3LYP method.

  15. Is dipole moment a valid descriptor of excited state's charge-transfer character?

    PubMed

    Petelenz, Piotr; Pac, Barbara

    2013-11-20

    In the ongoing discussion on excited states of the pentacene crystal, dipole moment values have been recently invoked to gauge the CT admixture to excited states of Frenkel parentage in a model cluster. In the present paper, a simple dimer model is used to show that, in general, the dipole moment is not a valid measure of the CT contribution. This finding eliminates some apparent disagreement between the computational results published by different research groups. The implications of our results and other related aspects of cluster-type quantum chemistry calculations are discussed in the context of the standing literature dispute concerning the mechanism of singlet fission in the pentacene crystal, notably the role of charge transfer contributions vs the involvement of an excimer-like doubly excited intermediate (D state).

  16. Estimation of ground and excited state dipole moments of Oil Red O by solvatochromic shift methods.

    PubMed

    Sıdır, İsa; Gülseven Sıdır, Yadigar

    2015-01-25

    Absorption and fluorescence spectra of Oil Red O (abbreviated as ORO) are recorded in various solvents with different polarity in the range of 250-900 nm, at room temperature. The solvatochromic shift methods have been used to determine the ground state (μg) and excited state (μe) dipole moments depending on dielectric constant and refractive index functions. It is observed that fluorescence spectra show positive solvatochromism whereas absorption spectra do not indicates sensitive behavior to solvent polarity. Excited state dipole moment is found as higher than those of ground state for all of the used methods and it is attributed to more polar excited state of ORO. Theoretical μg has been determined by quantum chemical calculations using DFT and semi empirical methods. HOMO, LUMO, molecular electrostatic potential (MEP) and solvent accessible surface of ORO are calculated by using DFT-B3LYP method.

  17. Excited-State Dipole and Quadrupole Moments: TD-DFT versus CC2

    PubMed Central

    2016-01-01

    The accuracies of the excited-state dipole and quadrupole moments obtained by TD-DFT are assessed by considering 16 different exchange-correlation functionals and more than 30 medium and large molecules. Except for excited-state presenting a significant charge-transfer character, a relatively limited dependency on the nature of the functional is found. It also turns out that while DFT ground-state dipole moments tend to be too large, the reverse trend is obtained for their excited-state counterparts, at least when hybrid functionals are used. Consequently, the TD-DFT excess dipole moments are often too small, an error that can be fortuitously corrected for charge-transfer transition by selecting a pure or a hybrid functional containing a small share of exact exchange. This error-cancelation phenomena explains the contradictory conclusions obtained in previous investigations. Overall, the largest correlation between CC2 and TD-DFT excess dipoles is obtained with M06-2X, but at the price of a nearly systematic underestimation of this property by ca. 1 D. For the excess quadrupole moments, the average errors are of the order of 0.2–0.6 D·Å for the set of small aromatic systems treated. PMID:27385324

  18. Excited-State Dipole and Quadrupole Moments: TD-DFT versus CC2.

    PubMed

    Jacquemin, Denis

    2016-08-09

    The accuracies of the excited-state dipole and quadrupole moments obtained by TD-DFT are assessed by considering 16 different exchange-correlation functionals and more than 30 medium and large molecules. Except for excited-state presenting a significant charge-transfer character, a relatively limited dependency on the nature of the functional is found. It also turns out that while DFT ground-state dipole moments tend to be too large, the reverse trend is obtained for their excited-state counterparts, at least when hybrid functionals are used. Consequently, the TD-DFT excess dipole moments are often too small, an error that can be fortuitously corrected for charge-transfer transition by selecting a pure or a hybrid functional containing a small share of exact exchange. This error-cancelation phenomena explains the contradictory conclusions obtained in previous investigations. Overall, the largest correlation between CC2 and TD-DFT excess dipoles is obtained with M06-2X, but at the price of a nearly systematic underestimation of this property by ca. 1 D. For the excess quadrupole moments, the average errors are of the order of 0.2-0.6 D·Å for the set of small aromatic systems treated.

  19. Carrier concentration dependence of the tunability of the dipole resonance peak in optically excited metamaterials

    NASA Astrophysics Data System (ADS)

    Chatzakis, Ioannis; Luo, Liang; Wang, Jigang; Shen, Nian Hai; Koschny, Thomas; Soukoulis, Costas

    2011-03-01

    Currently, there is strong interest to explore the dynamic control of the electromagnetic properties of metamaterials, which have important implications on their optoelectronic applications. While the design, fabrication and photo-doping of metamaterial/semiconductor structures have been actively pursued, some fundamental issues related to highly photo-excited states, their dynamic tuning and temporal evolution remain open. Using optical-pump terahertz probe spectroscopy, we report on the pump fluence dependence of the electric dipole resonance tunability in metamaterials. We find a previously undiscovered large non-monotonic variation on the strength of the dipole resonance peak with the photo-injected carrier concentration.

  20. Tailoring magnetic energies to form dipole skyrmions and skyrmion lattices

    NASA Astrophysics Data System (ADS)

    Montoya, S. A.; Couture, S.; Chess, J. J.; Lee, J. C. T.; Kent, N.; Henze, D.; Sinha, S. K.; Im, M.-Y.; Kevan, S. D.; Fischer, P.; McMorran, B. J.; Lomakin, V.; Roy, S.; Fullerton, E. E.

    2017-01-01

    The interesting physics and potential memory technologies resulting from topologically protected spin textures such as skyrmions have prompted efforts to discover new material systems that can host these kinds of magnetic structures. Here, we use the highly tunable magnetic properties of amorphous Fe/Gd multilayer films to explore the magnetic properties that lead to dipole-stabilized skyrmions and skyrmion lattices that form from the competition of dipolar field and exchange energy. Using both real space imaging and reciprocal space scattering techniques, we determined the range of material properties and magnetic fields where skyrmions form. Micromagnetic modeling closely matches our observation of small skyrmion features (˜50 to 70 nm) and suggests that these classes of skyrmions have a rich domain structure that is Bloch-like in the center of the film and more Néel-like towards each surface. Our results provide a pathway to engineer the formation and controllability of dipole skyrmion phases in a thin film geometry at different temperatures and magnetic fields.

  1. Low-cost, pseudo-Halbach dipole magnets for NMR

    NASA Astrophysics Data System (ADS)

    Tayler, Michael C. D.; Sakellariou, Dimitrios

    2017-04-01

    We present designs for compact, inexpensive and strong dipole permanent magnets aimed primarily at magnetic resonance applications where prepolarization and detection occur at different locations. Low-homogeneity magnets with a 7.5 mm bore size and field up to nearly 2 T are constructed using low-cost starting materials, standard workshop tools and only few hours of labor - an achievable project for a student or postdoc with spare time. As an application example we show how our magnet was used to polarize the nuclear spins in approximately 1 mL of pure [13C ]-methanol prior to detection of its high-resolution NMR spectrum at zero field (measurement field below 10-10 T), where signals appear at multiples of the carbon-hydrogen spin-spin coupling frequency 1JCH = 140.7 (1) Hz.

  2. Low-cost, pseudo-Halbach dipole magnets for NMR.

    PubMed

    Tayler, Michael C D; Sakellariou, Dimitrios

    2017-04-01

    We present designs for compact, inexpensive and strong dipole permanent magnets aimed primarily at magnetic resonance applications where prepolarization and detection occur at different locations. Low-homogeneity magnets with a 7.5mm bore size and field up to nearly 2T are constructed using low-cost starting materials, standard workshop tools and only few hours of labor - an achievable project for a student or postdoc with spare time. As an application example we show how our magnet was used to polarize the nuclear spins in approximately 1mL of pure [(13)C]-methanol prior to detection of its high-resolution NMR spectrum at zero field (measurement field below 10(-10)T), where signals appear at multiples of the carbon-hydrogen spin-spin coupling frequency (1)JCH=140.7(1)Hz.

  3. Pair Cascades and Deathlines in Offset Magnetic Dipole Fields

    NASA Technical Reports Server (NTRS)

    Harding, Alice; Muslimov, Alex

    2010-01-01

    We investigate electron-positron pair cascades in a dipole magnetic field whose axis is offset from the neutron star center. In such a field geometry, the polar cap is displaced from the neutron star symmetry axis and the field line radius of curvature is modified. Using the modified parallel electric field near the polar cap of an offset dipole, we simulate pair cascades to determine the pair deathlines and pair multiplicities as a function of the offset parameter. We find that the pair multiplicity can change dramatically with a modest offset, with a significant increase on one side of the polar cap. Lower pair deathlines allow a larger fraction of the pulsar population, that include old and millisecond pulsars, to produce cascades with high multiplicity.

  4. 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.

  5. 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.

  6. 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.

  7. Measurement of the magnetic-field parameters of the NICA Booster dipole magnet

    NASA Astrophysics Data System (ADS)

    Kostromin, S. A.; Borisov, V. V.; Bichkov, A. V.; Golubitsky, O. M.; Donyagin, A. N.; Morozov, N. A.; Samsonov, E. V.; Omelyanenko, M. M.; Khodzhibagiyan, H. G.; Shemchuk, A. V.

    2016-12-01

    Serial assembly and tests of dipole and quadrupole magnets of the NICA Booster have started at the Laboratory of High Energy Physics of the Joint Institute for Nuclear Research (JINR). The accelerator is fitted with Nuclotron-type magnets with a superconducting winding and an iron yoke for shaping the needed magnetic field. The design of magnets for NICA was optimized (based on the experience gained in constructing and operating the JINR Nuclotron) for the production of magnetic fields of the required configuration in terms of the beam dynamics in the accelerator and the collider. Measurements of parameters of the field of each magnet are expected to be performed in the process of assembly and testing of each module of the magnet-cryostat system of the NICA Booster and Collider. The results of magnetic measurements for the NICA Booster dipole magnet are presented.

  8. Isovector and isoscalar dipole excitations in 9Be and 10Be studied with antisymmetrized molecular dynamics

    NASA Astrophysics Data System (ADS)

    Kanada-En'yo, Yoshiko

    2016-02-01

    Isovector and isoscalar dipole excitations in 9Be and 10Be are investigated in the framework of antisymmetrized molecular dynamics, in which angular-momentum and parity projections are performed. In the present method, 1p-1h excitation modes built on the ground state and a large amplitude α -cluster mode are taken into account. The isovector giant dipole resonance (GDR) in E >20 MeV shows the two-peak structure, which is understood from the dipole excitation in the 2 α core part with the prolate deformation. Because of valence neutron modes against the 2 α core, low-energy E 1 resonances appear in E <20 MeV, exhausting about 20 % of the Thomas-Reiche-Kuhn sum rule and 10 % of the calculated energy-weighted sum. The dipole resonance at E ˜15 MeV in 10Be can be interpreted as the parity partner of the ground state having a 6He+α structure and has remarkable E 1 strength because of the coherent contribution of two valence neutrons. The isoscalar dipole strength for some low-energy resonances is significantly enhanced by the coupling with the α -cluster mode. For the E 1 strength of 9Be, the calculation overestimates the energy-weighted sum (EWS) in the low-energy (E <20 MeV) and GDR (20

  9. OSCILLATOR STRENGTHS OF VIBRIONIC EXCITATIONS OF NITROGEN DETERMINED BY THE DIPOLE (γ, γ) METHOD

    SciTech Connect

    Liu, Ya-Wei; Kang, Xu; Xu, Long-Quan; Ni, Dong-Dong; Zhu, Lin-Fan; Yang, Ke; Hiraoka, Nozomu; Tsuei, Ku-Ding E-mail: yangke@sinap.ac.cn

    2016-03-10

    The oscillator strengths of the valence-shell excitations of molecular nitrogen have significant applicational values in studies of the Earth's atmosphere and interstellar gases. In this work, the absolute oscillator strengths of the valence-shell excitations of molecular nitrogen in 12.3–13.4 eV were measured by the novel dipole (γ, γ) method, in which the high-resolution inelastic X-ray scattering is operated at a negligibly small momentum transfer and can simulate the photoabsorption process. Because the experimental technique used in the present work is distinctly different from those used previously, the present experimental results give an independent cross-check to previous experimental and theoretical data. The excellent coincidence of the present results with the dipole (e, e) and those that were extrapolated indicates that the present oscillator strengths can serve as benchmark data.

  10. Collisional excitation of the highly excited hydrogen atoms in the dipole form of the semiclassical impact parameter and Born approximations

    NASA Technical Reports Server (NTRS)

    Omidvar, K.

    1971-01-01

    Expressions for the excitation cross section of the highly excited states of the hydrogenlike atoms by fast charged particles have been derived in the dipole approximation of the semiclassical impact parameter and the Born approximations, making use of a formula for the asymptotic expansion of the oscillator strength of the hydrogenlike atoms given by Menzel. When only the leading term in the asymptotic expansion is retained, the expression for the cross section becomes identical to the expression obtained by the method of the classical collision and correspondence principle given by Percival and Richards. Comparisons are made between the Bethe coefficients obtained here and the Bethe coefficients of the Born approximation for transitions where the Born calculation is available. Satisfactory agreement is obtained only for n yields n + 1 transitions, with n the principal quantum number of the excited state.

  11. 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.

  12. Low lying electric dipole excitations in nuclei of the rare earth region

    SciTech Connect

    von Brentano, P.; Zilges, A.; Herzberg, R.D. . Inst. fuer Kernphysik); Zamfir, N.V. ); Kneissl, U.; Heil, R.D.; Pitz, H.H. . Inst. fuer Strahlenphysik); Wesselborg, C. . Inst. fuer Kernphysik)

    1992-01-01

    From many experiments with low energy photon scattering on deformed rare earth nuclei we have obtained detailed information about the distribution of electric dipole strength below 4 MeV. Apart from some weaker transitions between 2 and 4 MeV we observed one, and sometimes two, very strong El-groundstate transitions around 1.5 MeV in all examined nuclei. They arise from the de-excitation of the bandheads of the (J[sup [pi

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

    PubMed

    Kambe, Takashi; Oshima, Kokichi

    2014-09-19

    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.

  14. 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.

  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. Ultrafast optical excitation of magnetic skyrmions

    PubMed Central

    Ogawa, N.; Seki, S.; Tokura, Y.

    2015-01-01

    Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures. PMID:25897634

  17. Radiation efficiency for exciting whistler modes of electric and magnetic antennas: a comparison

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    Low frequency whistler modes (ω <ωc / 2) are excited in a large uniform laboratory plasma with electric dipoles and magnetic loop antennas oriented perpendicular to the ambient magnetic field. The antennas are driven under identical plasma conditions with short pulses from the same rf source so as to avoid nonlinear effects. The wave propagation and rf field topology are measured with rf probes. As expected, a magnetic loop antenna excites much stronger whistler modes than an electric dipole antenna. This is because the dipole electric field is shielded by sheaths and its current is a small displacement current compared to the conduction current of a closed loop antenna. A power ratio of Ploop /Pdipole = 8000 has been observed. The radiation resistances have also been obtained from first principles (Rrad =Prad /Irms2), but cannot be compared since the currents are vastly different. It is interesting to note that the electric dipole excites a wave whose topology resembles that of an m = 1 helicon mode. The loop has an elongated shape of the same length as the electric dipole (15 cm) and excites an m = 0 mode. These results are relevant to whistler wave injections experiments into space plasmas. Work supported by NSF/DOE.

  18. Hydrogen atom excitation in intense attosecond laser field: Gauge dependence of dipole approximation

    SciTech Connect

    Aldarmaa, Ch. E-mail: l-xemee@yahoo.com; Khenmedekh, L. E-mail: l-xemee@yahoo.com; Lkhagva, O.

    2014-03-24

    It is assumed that, the atomic excitations probability can be calculated using first order perturbation theory and dipole approximations. The validity of the dipole approximations had been examined by comparing the results with the results obtained by exact calculations within the first order perturbation theory[2]. Figure 1 shows the time dependence of the transition probability in the dipole approximation. From these plots it is obvious that, the probabilities obtained in the length gauge are higher than that in the velocity gauge, in the interaction period (−τ/2dipole approximation) calculations results. (Figure 2) Though the time evolution of the same transition probabilities are different for these cases, the final results are the same for all three cases, excluding the 6s-6p{sub 0} transition. For the later case, only the length gauge give a false results, but the velocity gauge give the same result as the exact one, for the final value of the transition probability.

  19. Study on magnetic field deviation due to manufacturing errors of the SIS100 superconducting dipole magnet

    NASA Astrophysics Data System (ADS)

    Sugita, Kei; Fischer, Egbert; Mierau, Anna; Roux, Christian; Schnizer, Pierre

    2016-12-01

    An international accelerator project, Facility for Antiproton and Ion Research in Europe (FAIR), is being constructed at Darmstadt, Germany. Central part of the accelerator chain is a superconducting heavy ion synchrotron SIS100, which accelerates injected particles from existing synchrotron SIS18, and provides them to experiment sites and further accelerators. Superconducting magnets in SIS100 are mainly superferric magnet with a Nuclotron cable. After R&D, the First of Series (FoS) main dipole magnet has been manufactured and tested successfully. However, magnetic field quality is unsatisfactory. We report on the investigation of the magnetic field quality by means of magnetic field measurements, geometrical measurements, and electromagnetic simulations.

  20. Magnetic Excitation for Spin Vibration Testing

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter; Mehmed, Oral; Brown, Gerald V.

    1997-01-01

    The Dynamic Spin Rig Laboratory (DSRL) at the NASA Lewis Research Center is a facility used for vibration testing of structures under spinning conditions. The current actuators used for excitation are electromagnetic shakers which are configured to apply torque to the rig's vertical rotor. The rotor is supported radially and axially by conventional bearings. Current operation is limited in rotational speed, excitation capability, and test duration. In an effort to enhance its capabilities, the rig has been initially equipped with a radial magnetic bearing which provides complementary excitation and shaft support. The new magnetic feature has been used in actual blade vibration tests and its performance has been favorable. Due to the success of this initial modification further enhancements are planned which include making the system fully magnetically supported. This paper reports on this comprehensive effort to upgrade the DSRL with an emphasis on the new magnetic excitation capability.

  1. 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.

  2. Advances in the transient dc photocurrent technique for excited state dipole moment measurements

    SciTech Connect

    Smirnov, S.N.; Braun, C.L.

    1998-08-01

    Recent advances in the transient dc photocurrent technique for measuring excited state dipole moments, developed in our group, are discussed. A variety of approaches with detailed analyses of their advantages and disadvantages including cell design, circuit construction tricks, the data acquisition procedure, calibration, and the theoretical treatment of different conditions, are presented. Sensitivity, time resolution limitations, and newly developed features, such as the signal{close_quote}s dependence on light polarization as well as charge separation at interfaces are outlined. Dipole moments of a few molecules (diphenylcyclopropenone, bianthryl, dimethylaminonitrostilbene, Coumarin 153, and fluoroprobe) suitable for calibration purpose are reported{emdash}some of them for the first time. {copyright} {ital 1998 American Institute of Physics.}

  3. Dipole moment of aniline in the excited S 1 state from thermochromic effect on electronic spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2005-11-01

    Using the thermochromic shift method of absorption and fluorescence spectra of aniline in ethyl acetate for temperature ranging from 213 to 393 K, the change of the dipole moment Δ μ = μe - μg = 0.84 D between the ground and first excited singlet state was determined based on the Bilot and Kawski theory. This is in agreement with the result obtained by Lombardi from optical Stark effect in the rotational fine structure. For the known dipole moment in the ground state μg = 1.53 D and for α/ a3 = 0.483 ( α is the polarizability and a is the Onsager interaction radius of the solute) the average value of μe = 2.37 D and a = 2.7 Å were determined. The values obtained for aniline are compared with the experimental values determined by other authors.

  4. Dipole moment of benzonitrile in its excited S 1 state from thermochromic shifts of fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-02-01

    The effect of temperature T ranging from 293 to 393 K on absorption and fluorescence spectra of benzonitrile (BN) in ethyl acetate is studied. The absorption spectra of BN remain unchanged with increasing T. The analysis of fluorescence band shift by the Bilot and Kawski theory [L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621], for the known dipole moment value in the ground state μg = 4.18 D and α/ a3 = 0.5 ( α is the polarizability and a is the Onsager interaction radius of the solute), yield the average value of excited state dipole moment μe = 4.42 D. This value is in satisfactory agreement with 4.45, 4.51 and 4.57 D obtained previously from the Stark shift of rotational lines.

  5. Protocol for observing molecular dipole excitations by attosecond self-streaking

    NASA Astrophysics Data System (ADS)

    Wachter, Georg; Nagele, Stefan; Sato, Shunsuke A.; Pazourek, Renate; Wais, Michael; Lemell, Christoph; Tong, Xiao-Min; Yabana, Kazuhiro; Burgdörfer, Joachim

    2015-12-01

    We propose a protocol to probe the ultrafast evolution and dephasing of coherent electronic excitation in molecules in the time domain by the intrinsic streaking field generated by the molecule itself. Coherent electronic motion in the endohedral fullerene Ne@C 60 is initiated by a moderately intense femtosecond UV-visible pulse leading to coherent oscillations of the molecular dipole moment that persist after the end of the laser pulse. The resulting time-dependent molecular near field is probed through the momentum modulation of photoemission from the central neon atom by a time-delayed attosecond XUV pulse. Our ab initio time-dependent density functional theory and classical trajectory simulations predict that this self-streaking signal accurately traces the molecular dipole oscillations in real time. We discuss the underlying processes and give an analytical model that captures the essence of our ab initio simulations.

  6. Magnetic sensing via ultrasonic excitation

    NASA Astrophysics Data System (ADS)

    Yamada, Hisato; Takashima, Kazuya; Ikushima, Kenji; Toida, Hiraku; Sato, Michitaka; Ishizawa, Yoshiichi

    2013-04-01

    We present ultrasonic techniques for magnetic measurements. Acoustically modulated magnetization is investigated with sensitive rf detection by narrowband loop antennas. Magnetization on the surface of ferromagnetic metals is temporally modulated with the rf frequency of the irradiated ultrasonic waves, and the near-field components emitted from the focal point of the ultrasonic beam are detected. Based on the principle of the acoustically stimulated electromagnetic (ASEM) response, magnetic sensing and tomography are demonstrated by ultrasonic scanning. We show that ASEM imaging combines good acoustic resolution with magnetic contrast. The sensitivity of this method is estimated to be about 6 G/Hz1/2 in our current setup.

  7. Photophysical properties of thiadiazoles derivative: Estimation of ground and excited state dipole moments by theoretical and experimental approach

    NASA Astrophysics Data System (ADS)

    Muddapur, G. V.; Koppal, V. V.; Patil, N. R.; Melavanki, R. M.

    2016-05-01

    The absorption and fluorescence spectra of newly synthesized thiadiazole derivative namely 6-(4-chlorophenyl)-2-(naphthalene-1-ylmethyl) imidazo [2, 1-b][1,3,4] thiadiazole [6CNMT] have been recorded in various solvents of different polarities. The ground state dipole moment of 6CNMT was obtained from quantum chemical calculations. Solvatochromic correlations were used to estimate the ground state (μg) and excited state (μe) dipole moments. The excited state dipole moments are observed to be greater than the ground state dipole moment. Further, the changes in dipole moment (Δμ) were calculated both from solvatochromic shift method and microscopic solvent polarity parameter (ETN ) and the values are compared. The spectral variations were also analyzed by Kamlet-Taft parameters.

  8. 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.

  9. Controlling magnetic and electric dipole modes in hollow silicon nanocylinders.

    PubMed

    van de Haar, Marie Anne; van de Groep, Jorik; Brenny, Benjamin J M; Polman, Albert

    2016-02-08

    We propose a dielectric nanoresonator geometry consisting of hollow dielectric nanocylinders which support geometrical resonances. We fabricate such hollow Si particles with an outer diameter of 108-251 nm on a Si substrate, and determine their resonant modes with cathodo-luminescence (CL) spectroscopy and optical dark-field (DF) scattering measurements. The scattering behavior is numerically investigated in a systematic fashion as a function of wavelength and particle geometry. We find that the additional design parameter as a result of the introduction of a center gap can be used to control the relative spectral spacing of the resonant modes, which will enable additional control over the angular radiation pattern of the scatterers. Furthermore, the gap offers direct access to the enhanced magnetic dipole modal field in the center of the particle.

  10. Characterization and detection of oscillating magnetic dipole signals

    NASA Astrophysics Data System (ADS)

    Ram-Cohen, Tsuriel; Alimi, Roger; Weiss, Eyal; Zalevsky, Zeev

    2017-04-01

    The present paper deals with the problem of characterization of oscillating magnetic dipole (OMD) signals and the development of a suitable magnetic anomaly detection (MAD) algorithm for it. The resulting outcomes of investigating the above mentioned problem are: (1) a development of a complete model of the noise and the signal based on a non-linear gravity pendulum model. This model was compared and verified against real world magnetic signals, as well as simulated ones. (2) A detection algorithm that utilizes this model by whitening the noise and seeking for periodical features in the signal. The developed algorithm has high noise immunity with high detection probabilities even at as low SNR as  ‑10 dB. Compared to benchmark detectors, our detection scheme offers performance improved by 5–10 dB. Moreover, when testing the detector against real world signals, the SNR difference in respect to the performance predicted by the simulations was less than 2.5 dB.

  11. 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.

  12. 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.

  13. Positron-impact vibrational excitation cross sections and the Born dipole model

    NASA Astrophysics Data System (ADS)

    Marler, J. P.; Surko, C. M.; Gribakin, G. F.

    2006-05-01

    We describe in situ measurements of the positron- and electron-impact cross sections for vibrational excitation of the infrared-active (IR) ν3 mode in CF4 [1]. These cross sections are virtually identical and agree quantitatively with the predictions of the Born dipole model (BDM), which describes the effect of long range dipole coupling. We also compare the predictions of the BDM with the other positron-impact vibrational cross sections for IR modes measured to date (CO, CO2, H2, and CH4) [2]. The BDM contributions to the measured cross sections vary widely. However, for all molecules except H2 (for which the transition dipole moment is zero), the BDM model predicts the energy dependence of these cross sections quite well. The possible significance of these results will be discussed. [1] J.P. Marler and C.M. Surko, Phys. Rev. A. 72, 062702 (2005). [2] J.P. Marler, G.F. Gribakin and C.M. Surko, Nuclear Instrum. and Meth. B, in press (2006).

  14. 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.

  15. Double Photon Decay of the Electromagnetically Excited Double Giant Dipole Resonance in LEAD-208

    NASA Astrophysics Data System (ADS)

    Ritman, James Lambrecht

    In this work the electromagnetic excitation of high lying collective states has been studied in relativistic heavy ion collisions. The interaction in peripheral collisions is dominated by the exchange of high energy virtual photons. Heavy systems near 1cdotA GeV produce a virtual photon field that is highly luminous and of sufficiently short duration to enable the multiple excitation of Giant Resonances with high probability. In particular, the double excitation of the Giant Dipole Resonance (GDR) has been studied in this work by measuring the photons emitted in peripheral reactions with the system 1.A GeV ^ {209}Bi on ^{208} Pb. This study concentrated on the photon decay of Coulomb excited collective states. Despite the relatively small ground state gamma-decay branching ratio, investigation of this channel provides several advantages compared to measuring statistical particle decay. The most important advantage is the strong enhancement of E1 transitions with respect to higher multipolarities; therefore, study of gamma-decay provides a highly selective measurement of the GDR. Photons in the Giant Resonance region were measured both as singles and as gamma- gamma pairs. For symmetry reasons the target and projectile nuclei can be mutually Coulomb excited. In order to insure that both photons in the gamma -gamma pairs came from the same nucleus, the large Doppler shift of photons emitted from the moving projectile has been exploited. Appropriate placement of the gamma detectors permitted a complete separation of the GDR photons emitted by either the target or projectile nucleus. This work provides the first experimental evidence of the gamma-gamma decay of the Coulomb excited double GDR (GDR2). The position of the resonance indicates harmonicity of the T_{<} multi-GDR. However, the increase of the GDR2 width over the GDR's width by only about a factor of sqrt{2} is significantly less than expected. Finally, the GDR2 excitation cross section is compared with model

  16. Systematic investigation of the low-energy dipole excitations in 176,178,180Hf within rotational, translational and Galilean invariant quasiparticle RPA

    NASA Astrophysics Data System (ADS)

    Guliyev, E.; Kuliev, A. A.; Ertugral, F.

    2013-10-01

    Low-energy magnetic and electric dipole excitations in the even-even isotopes 176-180Hf have been systematically studied within the rotational, translational and Galilean invariant Quasiparticle Random Phase Approximation (QRPA). The results of the calculations show that most of the states predicted to have magnetic character and the computed M1 strength in these nuclei is less strongly fragmented than in mid-shell isotopes. The results of the calculations are in good agreement with experimental data. The results of the calculations indicate the presence of a few prominent negative parity dipole K=1 states in the energy investigated region. The comparison of the calculations with the available experimental data makes possible the interpretation of the states where parity could not be assigned experimentally.

  17. Emission quenching of magnetic dipole transitions near an absorbing nanoparticle (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chigrin, Dmitry N.; Kumar, Deepu; von Plessen, Gero

    2016-09-01

    Emission quenching is analysed at nanometer distances from the surface of an absorbing nanoparticle. It is demonstrated that emission quenching at small distances to the surface is much weaker for magnetic-dipole (MD) than for electric-dipole (ED) transitions. This difference is explained by the fact that the electric field induced by a magnetic dipole has a weaker distance dependence than the electric field of an electric dipole. It is also demonstrated that in the extreme near-field regime the non-locality of the optical response of the metal results in additional emission quenching for both ED and MD transitions.

  18. Sign Changes in the Electric Dipole Moment of Excited States in Rubidium-Alkaline Earth Diatomic Molecules

    NASA Astrophysics Data System (ADS)

    Pototschnig, Johann V.; Lackner, Florian; Hauser, Andreas W.; Ernst, Wolfgang E.

    2015-06-01

    In a recent series of combined experimental and theoretical studies we investigated the ground state and several excited states of the Rb-alkaline earth molecules RbSr and RbCa. The group of alkali-alkaline earth (AK-AKE) molecules has drawn attention for applications in ultracold molecular physics and the measurement of fundamental constants due to their large permanent electric and magnetic dipole moments in the ground state. These properties should allow for an easy manipulation of the molecules and simulations of spin models in optical lattices. In our studies we found that the permanent electric dipole moment points in different directions for certain electronically excited states, and changes the sign in some cases as a function of bond length. We summarize our results, give possible causes for the measured trends in terms of molecular orbital theory and extrapolate the tendencies to other combinations of AK and AKE - elements. F. Lackner, G. Krois, T. Buchsteiner, J. V. Pototschnig, and W. E. Ernst, Phys. Rev. Lett., 2014, 113, 153001; G. Krois, F. Lackner, J. V. Pototschnig, T. Buchsteiner, and W. E. Ernst, Phys. Chem. Chem. Phys., 2014, 16, 22373; J. V. Pototschnig, G. Krois, F. Lackner, and W. E. Ernst, J. Chem. Phys., 2014, 141, 234309 J. V. Pototschnig, G. Krois, F. Lackner, and W. E. Ernst, J. Mol. Spectrosc., in Press (2015), doi:10.1016/j.jms.2015.01.006 M. Kajita, G. Gopakumar, M. Abe, and M. Hada, J. Mol. Spectrosc., 2014, 300, 99-107 A. Micheli, G. K. Brennen, and P. Zoller, Nature Physics, 2006, 2, 341-347

  19. Spectroscopy of magnetic excitations in magnetic superconductors using vortex motion.

    PubMed

    Bulaevskii, L N; Hruska, M; Maley, M P

    2005-11-11

    In magnetic superconductors a moving vortex lattice is accompanied by an ac magnetic field which leads to the generation of spin waves. At resonance conditions the dynamics of vortices in magnetic superconductors changes drastically, resulting in strong peaks in the dc I-V characteristics at voltages at which the washboard frequency of the vortex lattice matches the spin wave frequency omegaS(g), where g are the reciprocal vortex lattice vectors. We show that if the washboard frequency lies above the magnetic gap, measurement of the I-V characteristics provides a new method to obtain information on the spectrum of magnetic excitations in borocarbides and cuprate layered magnetic superconductors.

  20. Elementary spin excitations in ultrathin itinerant magnets

    NASA Astrophysics Data System (ADS)

    Zakeri, Khalil

    2014-12-01

    Elementary spin excitations (magnons) play a fundamental role in condensed matter physics, since many phenomena e.g. magnetic ordering, electrical (as well as heat) transport properties, ultrafast magnetization processes, and most importantly electron/spin dynamics can only be understood when these quasi-particles are taken into consideration. In addition to their fundamental importance, magnons may also be used for information processing in modern spintronics. Here the concept of spin excitations in ultrathin itinerant magnets is discussed and reviewed. Starting with a historical introduction, different classes of magnons are introduced. Different theoretical treatments of spin excitations in solids are outlined. Interaction of spin-polarized electrons with a magnetic surface is discussed. It is shown that, based on the quantum mechanical conservation rules, a magnon can only be excited when a minority electron is injected into the system. While the magnon creation process is forbidden by majority electrons, the magnon annihilation process is allowed instead. These fundamental quantum mechanical selection rules, together with the strong interaction of electrons with matter, make the spin-polarized electron spectroscopies as appropriate tools to excite and probe the elementary spin excitations in low-dimensional magnets e.g ultrathin films and nanostructures. The focus is put on the experimental results obtained by spin-polarized electron energy loss spectroscopy and spin-polarized inelastic tunneling spectroscopy. The magnon dispersion relation, lifetime, group and phase velocity measured using these approaches in various ultrathin magnets are discussed in detail. The differences and similarities with respect to the bulk excitations are addressed. The role of the temperature, atomic structure, number of atomic layers, lattice strain, electronic complexes and hybridization at the interfaces are outlined. A possibility of simultaneous probing of magnons and phonons

  1. Solar rotating magnetic dipole?. [around axis perpendicular to rotation axis of the sun

    NASA Technical Reports Server (NTRS)

    Antonucci, E.

    1974-01-01

    A magnetic dipole rotating around an axis perpendicular to the rotation axis of the sun can account for the characteristics of the surface large-scale solar magnetic fields through the solar cycle. The polarity patterns of the interplanetary magnetic field, predictable from this model, agree with the observed interplanetary magnetic sector structure.

  2. Magnetic Moments of Excited Baryons

    NASA Astrophysics Data System (ADS)

    Metag, Volker

    2017-01-01

    In project A.3, the reaction γ p → π0γ'p has been studied using the TAPS photon spectrometer in the energy range √s= 1221-1331 MeV. Energy tagged photon beams have been produced with the Glasgow tagging spectrometer from electron beams provided by the MAMI-B accelerator. Angle and energy differential cross sections have been measured and compared to theoretical calculations. This comparison allows the magnetic moment of the Δ+ isobar to be extracted for the first time to μΔ+ = [2.7+1.3-1.0(stat)±1.5(syst)±3(theo)] μN. In an extension of the A3 project to the meson sector, the time-like transition form factor of the η meson has been measured with the Crystal Ball/TAPS detector system at MAMI-C.

  3. 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.

  4. Direct detection of light anapole and magnetic dipole DM

    SciTech Connect

    Nobile, Eugenio Del; Gelmini, Graciela B.; Huh, Ji-Haeng; Gondolo, Paolo E-mail: gelmini@physics.ucla.edu E-mail: jhhuh@physics.ucla.edu

    2014-06-01

    We present comparisons of direct detection data for ''light WIMPs'' with an anapole moment interaction (ADM) and a magnetic dipole moment interaction (MDM), both assuming the Standard Halo Model (SHM) for the dark halo of our galaxy and in a halo-independent manner. In the SHM analysis we find that a combination of the 90% CL LUX and CDMSlite limits or the new 90% CL SuperCDMS limit by itself exclude the parameter space regions allowed by DAMA, CoGeNT and CDMS-II-Si data for both ADM and MDM. In our halo-independent analysis the new LUX bound excludes the same potential signal regions as the previous XENON100 bound. Much of the remaining signal regions is now excluded by SuperCDMS, while the CDMSlite limit is much above them. The situation is of strong tension between the positive and negative search results both for ADM and MDM. We also clarify the confusion in the literature about the ADM scattering cross section.

  5. Electronically excited dipole moment of 4-aminobenzonitrile from thermochromic absorption and fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-07-01

    The effect of temperature on absorption and fluorescence spectra of 4-aminobenzonitrile (ABN) in 1,2-dichloroethane is studied for temperature ranging from 296 K to 343 K. The analysis of absorption and fluorescence band shift on the basis of Bilot and Kawski theory [L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621], for the known dipole moment in the ground state μg = 5.92 D, and α/ a3 = 0.5 ( α is the polarizability and a is the Onsager interaction radius of the solute) yields for ABN: (1) the empirical Onsager interaction radius a = 3.3 Å, (2) the dipole moment in the excited S 1 state μe = 7.14 D which agrees very well with the value of μe = 7.20 D obtained by Borst et al. [D.R. Borst, T.M. Korter, D.W. Pratt, Chem. Phys. Lett. 350 (2001) 485] from Stark effect studies. Both values of μe concern free ABN molecule and differ significantly from the values of μg (8.0 D, 8.5 D and 8.3 D in cyclohexane, benzene and 1,4-dioxane, respectively) obtained by Schuddeboom et al. [W. Schuddeboom, S.A. Jonker, J.M. Warman, U. Leinhos, W. Kühnle, K.A. Zachariasse, J. Phys. Chem. 96 (1992) 10809] from the time-resolved microwave conductivity measurements which are solvent-dependent. The group moment additivity law in the case of ABN molecule is approximately applicable, both in the ground and in the excited electronic state.

  6. 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).

  7. Magnetic Excitations from Stripes in Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-03-01

    While it is generally believed that antiferromagnetic spin excitations play a significant role in the pairing mechanism of copper-oxide superconductors [1], the nature of the magnetic excitations themselves remains a matter of controversy. Recent measurements of the dispersion of spin excitations in superconducting YBa_2Cu_3O_6+x (YBCO) have attracted much attention. Here we present the results of comprehensive inelastic neutron scattering measurements of the momentum- and energy-dependent spectra of the magnetic fluctuations in La_0.875Ba_0.125CuO_4, which exhibits inhomogeneous, charge-stripe order. We will also point out universalities and differences in the magnetic excitation spectra compared to related charge-stripe ordered compounds and high-temperature superconductors, including La_2-xSr_xNiO4 and YBCO. JMT, HW, GDG and GX are supported by U.S. Department of Energy contract # DE-AC02-98CH1088 [1] J. Orenstein and A. J. Millis, Science 288, 468 (2000).

  8. Solvent Effects on the Electronic Absorption and Fluorescence Spectra of HNP: Estimation of Ground and Excited State Dipole Moments.

    PubMed

    Desai, Vani R; Hunagund, Shirajahammad M; Basanagouda, Mahantesha; Kadadevarmath, Jagadish S; Sidarai, Ashok H

    2016-07-01

    We report the effect of solvents on absorption and fluorescence spectra of biologically active 3(2H)-pyridazinone namely 5-(2-hydroxy-naphthalen-1-yl)-2-phenyl-2H-pyridazin-3-one (HNP) in different solvents at room temperature. The ground and the excited state dipole moments of HNP molecule was estimated from Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations using the solvatochromic shift method. The ground state dipole moment (μ g ) was also estimated by Guggenheim and Higasi method using the dielectric constant and refractive index of solute at different concentrations, the μ g value obtained from these two methods are comparable to the μ g value obtained by the solvatochromic shift method. The excited state dipole moment (μ e ) is greater than the ground state dipole moment (μ g ), which indicates that the excited state is more polar than the ground state. Further, we have evaluated the change in dipole moment (Δμ) from the solvatochromic shift method and on the basis of molecular-microscopic solvent polarity parameter[Formula: see text], later on the values were compared.

  9. Resonant photoelectron imaging of deprotonated uracil anion via vibrational levels of a dipole-bound excited state

    NASA Astrophysics Data System (ADS)

    Huang, Dao-Ling; Liu, Hong-Tao; Ning, Chuan-Gang; Dau, Phuong Diem; Wang, Lai-Sheng

    2017-01-01

    We report both non-resonant and resonant high-resolution photoelectron imaging of cryogenically-cooled deprotonated uracil anions, N1[U-H]-, via vibrational levels of a dipole-bound excited state. Photodetachment spectroscopy of N1[U-H]- was reported previously (Liu et al., 2014), in which forty-six vibrational autodetachment resonances due to the excited dipole-bound state were observed. By tuning the detachment laser to the vibrational levels of the dipole-bound state, we obtained high-resolution resonant photoelectron spectra, which are highly non-Franck-Condon. The resonant photoelectron spectra reveal many Franck-Condon inactive vibrational modes, significantly expanding the capability of photoelectron spectroscopy. A total of twenty one fundamental vibrational frequencies for the N1[U-H]rad radical are obtained, including all eight low-frequency out-of-plane modes, which are forbidden in non-resonant photoelectron spectroscopy. Furthermore, the breakdown of the Δv = -1 propensity rule is observed for autodetachment from many vibrational levels of the dipole-bound state, due to anharmonic effects. In particular, we have observed intramolecular electron rescattering in a number of resonant photoelectron spectra, leading to excitations of low-frequency vibrational modes. Further theoretical study may be warranted, in light of the extensive experimental data and new observations, to provide further insight into the autodetachment dynamics and vibronic coupling in dipole-bound states, as well as electron molecule interactions.

  10. BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE

    SciTech Connect

    Tycko, R.

    1984-10-01

    Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. The fixed points of the function and the stability of the fixed points are shown to determine the essential behavior of the scheme. Iterative schemes for broadband population inversion are treated in detail. Algebraic and numerical methods for performing the mathematical analysis are presented. Two additional topics are treated. The first is the construction of sequences for uniform excitation of double-quantum coherence and for uniform polarization transfer over a range of spin couplings. Double-quantum excitation sequences are demonstrated in a liquid crystal system. The

  11. 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.

  12. 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.

  13. Magnetic dipole bands in 82Rb, 83Rb and 84Rb

    NASA Astrophysics Data System (ADS)

    Schwengner, R.; Schnare, H.; Frauendorf, S.; Dönau, F.; Käubler, 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.

    1998-12-01

    We have studied the isotopes 82Rb45, 83Rb46 and 84Rb47 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 11B+76Ge with E=50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a γ-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 82Rb and 84Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13-⩽Jπ⩽16-. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type π(fp)πg9/22νg9/2. This is the first evidence of magnetic rotation in the A≈80 region. In contrast, the M1 sequences in the odd-even nucleus 83Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.

  14. Nonlinear SU(2,1) Model of Multiple Giant Dipole Resonance Coulomb Excitation

    NASA Astrophysics Data System (ADS)

    Hussein, Mahir; de Toledo Piza, Antonio; Vorov, Oleg

    2000-10-01

    We construct a three-dimensional analytically soluble model of the nonlinear effects in Coulomb excitation of multiphonon Giant Dipole Resonances (GDR) based on the SU(2,1) algebra^1. Analytical expressions for the multi-phonon transition probabilities are derived. For reasonably small magnitude of nonlinearity x~= 0.15-0.3, the enhancement factor for the Double Giant Resonance excitation probabilities and the cross sections reaches values 1.3-2 compatible^1,2 with experimental data from relativistic ion collision experiments^3. The full 3-dimensional model predicts enhancement of the multiple GDR cross sections at low and high bombarding energies (with the minimum at ~= 1.3 GeV for the Pb+Pb colliding system). Enhancement factors for Double GDR measured in thirteen different processes with various projectiles and targets at different bombarding energies are well reproduced with the same value of the nonlinearity parameter with the exception of the anomalous case of ^136Xe which requires a larger value. The work has been supported by the FAPESP and by the CNPq. References ^1 M. S. Hussein, A. F. R. de Toledo Piza and O. K.Vorov, Ann. Phys. (N.Y.), 2000, to appear. ^2 M. S. Hussein, A. F. R. de Toledo Piza and O. K.Vorov, Phys. Rev. C59,R1242 (1999). ^3 T. Aumann, P.F. Bortignon, and H. Emling, Annu. Rev. Nucl. Part. Sci. 48, 351 (1998).

  15. Low lying electric dipole excitations in nuclei of the rare earth region

    SciTech Connect

    von Brentano, P.; Zilges, A.; Herzberg, R.D.; Zamfir, N.V.; Kneissl, U.; Heil, R.D.; Pitz, H.H.; Wesselborg, C.

    1992-10-01

    From many experiments with low energy photon scattering on deformed rare earth nuclei we have obtained detailed information about the distribution of electric dipole strength below 4 MeV. Apart from some weaker transitions between 2 and 4 MeV we observed one, and sometimes two, very strong El-groundstate transitions around 1.5 MeV in all examined nuclei. They arise from the de-excitation of the bandheads of the (J{sup {pi}},K)=(l{sup {minus}},0) and (J{sup {pi}},K)=(l{sup {minus}},1) octupole vibrational bands. It is shown that the decay branching ratios and the absolute transition strengths of these states can be reproduced rather well with an improved T(El)-operator in the sdf-Interacting Boson Model. Another class of octupole states has been investigated in the region of the semimagic nucleus {sup 142}Nd. Here a quintuplet of collective excitations around 3.5 MeV is expected due to the coupling of the 3{minus}-octupole vibration with the 2+-quadrupole vibration. We performed photon scattering experiments on the odd A neighboring nucleus {sup 141}Pr and found first evidence for the existence of 3{sup {minus}}{circle_times}2+{circle_times}particle-states.

  16. Evidence of dynamical dipole excitation in the fusion-evaporation of the 40Ca+152Sm heavy system

    NASA Astrophysics Data System (ADS)

    Parascandolo, C.; Pierroutsakou, D.; Alba, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Agodi, C.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; Inglima, G.; La Commara, M.; Martin, B.; Mazzocchi, C.; Mazzocco, M.; Rizzo, C.; Romoli, M.; Sandoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifirò, A.; Trimarchi, M.

    2016-04-01

    The excitation of the dynamical dipole mode along the fusion path was investigated for the first time in the formation of a heavy compound nucleus in the A ˜190 mass region. The compound nucleus was formed at identical conditions of excitation energy and spin from two entrance channels: the charge-asymmetric 40Ca+152Sm and the nearly charge-symmetric 48Ca+144Sm at Elab=11 and 10.1 MeV/nucleon, respectively. High-energy γ rays and light charged particles were measured in coincidence with evaporation residues by means of the MEDEA multidetector array (Laboratori Nazionali del Sud, Italy) coupled to four parallel plate avalanche counters. The charged particle multiplicity spectra and angular distributions were used to pin down the average excitation energy, the average mass, and the average charge of the compound nucleus. The γ -ray multiplicity spectrum and angular distribution related to the nearly charge-symmetric channel were employed to obtain new data on the giant dipole resonance in the compound nucleus. The dynamical dipole mode excitation in the charge-asymmetric channel was evidenced, in a model-independent way, by comparing the γ -ray multiplicity spectra and angular distributions of the two entrance channels with each other. Calculations of the dynamical dipole mode in the 40Ca+152Sm channel, based on a collective bremsstrahlung analysis of the reaction dynamics, are presented. Possible interesting implications in the superheavy-element quest are discussed.

  17. 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.

  18. 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

  19. Determination of the ground- and excited-state dipole moments of bromocresol purple in protic and aprotic solvents.

    PubMed

    Talone, Christopher J; Gao, Jingya; Lynch, James R; Tanu, Rhoda M; Deyrup, Stephen T

    2016-03-05

    Although it has been widely recognized that hydrogen bonds play a significant role in the photophysics of molecules, this phenomenon has rarely been applied to the solvatochromic method for determination of dipole moments. The difference in the dipole moment between the ground and excited state was determined in protic and aprotic solvents using both the Lippert-Mataga equation and the Bilot-Kawski equation for bromocresol purple, a molecule capable of hydrogen-bond donation and acceptance. The dipole change in protic environments was determined to be 15.2 ± 1.0 D for the Lippert-Mataga method and 9.2 ± 1.0 D for the Bilot-Kawski method, while the change in aprotic environments was 10.4 ± 1.0 D and 6.7 ± 1.0 D, respectively. Both methods highlighted the importance of hydrogen bonding in stabilizing increased charge-separation of the excited state, allowing for larger changes in dipole moments in protic environments. This study further validates a simple, rational modification to the commonly used methods that allows access to dipole-moment data on dyes with hydrogen-bonding capabilities through solvatochromic experiments.

  20. Determination of the ground- and excited-state dipole moments of bromocresol purple in protic and aprotic solvents

    NASA Astrophysics Data System (ADS)

    Talone, Christopher J.; Gao, Jingya; Lynch, James R.; Tanu, Rhoda M.; Deyrup, Stephen T.

    2016-03-01

    Although it has been widely recognized that hydrogen bonds play a significant role in the photophysics of molecules, this phenomenon has rarely been applied to the solvatochromic method for determination of dipole moments. The difference in the dipole moment between the ground and excited state was determined in protic and aprotic solvents using both the Lippert-Mataga equation and the Bilot-Kawski equation for bromocresol purple, a molecule capable of hydrogen-bond donation and acceptance. The dipole change in protic environments was determined to be 15.2 ± 1.0 D for the Lippert-Mataga method and 9.2 ± 1.0 D for the Bilot-Kawski method, while the change in aprotic environments was 10.4 ± 1.0 D and 6.7 ± 1.0 D, respectively. Both methods highlighted the importance of hydrogen bonding in stabilizing increased charge-separation of the excited state, allowing for larger changes in dipole moments in protic environments. This study further validates a simple, rational modification to the commonly used methods that allows access to dipole-moment data on dyes with hydrogen-bonding capabilities through solvatochromic experiments.

  1. Magnetization Dynamics in a Current-Driven Magnetic Nano-Pillar with Dipole-Dipole Coupling between Magnetic Layers (PREPRINT)

    DTIC Science & Technology

    2009-09-25

    gyromagnetic ratio. The structure of He! !,j will be clarified bellow. The second term a"( TD,j = M [Mj x [ Hef !,j x Mjll is dissipative torque that...nano-pillar looks as fol- lows: 8M· 8/ = "( [ Hef !,j x Mj ], j = 1,2. (2) The effective magnetic field Hef !,j for j-th layer, which enters the LLGS...equation, consists of the external bias magnetic field Hext and magnetodipolar fields, created by each of the two layers: 2 Hef !,j = Hext + L Hj,k

  2. 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.

  3. Collective excitation of an electric dipole on a molecular dimer in an organic dimer-Mott insulator.

    PubMed

    Itoh, K; Itoh, H; Naka, M; Saito, S; Hosako, I; Yoneyama, N; Ishihara, S; Sasaki, T; Iwai, S

    2013-03-08

    The terahertz response in 10-100 cm(-1) was investigated in an organic dimer-Mott (DM) insulator κ-(ET)(2)Cu(2)(CN)(3) that exhibits a relaxorlike dielectric anomaly. An ~30 cm(-1) band in the optical conductivity was attributable to collective excitation of the fluctuating intradimer electric dipoles that are formed by an electron correlation. We succeeded in observing photoinduced enhancement of this ~30 cm(-1) band, reflecting the growth of the electric dipole cluster in the DM phase. Such optical responses in κ-(ET)(2)Cu(2)(CN)(3) reflect an instability near the boundary between the DM-ferroelectric charge ordered phases.

  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. Reversals of the solar magnetic dipole in the light of observational data and simple dynamo models

    NASA Astrophysics Data System (ADS)

    Pipin, V. V.; Moss, D.; Sokoloff, D.; Hoeksema, J. T.

    2014-07-01

    Context. Observations show that the photospheric solar magnetic dipole usually does not vanish during the reversal of the solar magnetic field, which occurs in each solar cycle. In contrast, mean-field solar dynamo models predict that the dipole field does become zero. In a recent paper it was suggested that this contradiction could be explained as a large-scale manifestation of small-scale magnetic fluctuations of the surface poloidal field. Aims: Our aim is to confront this interpretation with the available observational data. Methods: Here we compare this interpretation with Wilcox Solar Observatory (WSO) photospheric magnetic field data in order to determine the amplitude of magnetic fluctuations required to explain the phenomenon and to compare the results with predictions from a simple dynamo model which takes these fluctuations into account. Results: We demonstrate that the WSO data concerning the magnetic dipole reversals are very similar to the predictions from our very simple solar dynamo model, which includes both mean magnetic field and fluctuations. The ratio between the rms value of the magnetic fluctuations and the mean field is estimated to be about 2, in reasonable agreement with estimates from sunspot data. The reversal epoch, during which the fluctuating contribution to the dipole is larger than that from the mean field, is about 4 months. The memory time of the fluctuations is about 2 months. Observations demonstrate that the rms of the magnetic fluctuations is strongly modulated by the phase of the solar cycle. This gives additional support to the concept that the solar magnetic field is generated by a single dynamo mechanism rather than also by independent small-scale dynamo action. A suggestion of a weak nonaxisymmetric magnetic field of a fluctuating nature arises from the analysis, with a lifetime of about 1 year. Conclusions: The behaviour of the magnetic dipole during the reversal epoch gives valuable information about details of solar

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

    DOE PAGES

    Khromova, Irina; Kužel, Petr; Brener, Igal; ...

    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

  7. Topological excitations in a kagome magnet.

    PubMed

    Pereiro, Manuel; Yudin, Dmitry; Chico, Jonathan; Etz, Corina; Eriksson, Olle; Bergman, Anders

    2014-09-08

    Chirality--that is, left or right handedness--is present in many scientific areas, and particularly in condensed matter physics. Inversion symmetry breaking relates chirality with skyrmions, which are protected field configurations with particle-like and topological properties. Here we show that a kagome magnet, with Heisenberg and Dzyaloshinskii-Moriya interactions, causes non-trivial topological and chiral magnetic properties. We also find that under special circumstances, skyrmions emerge as excitations, having stability even at room temperature. Chiral magnonic edge states of a kagome magnet offer, in addition, a promising way to create, control and manipulate skyrmions. This has potential for applications in spintronics, that is, for information storage or as logic devices. Collisions between these particle-like excitations are found to be elastic at very low temperature in the skyrmion-skyrmion channel, albeit without mass-conservation. Skyrmion-antiskyrmion collisions are found to be more complex, where annihilation and creation of these objects have a distinct non-local nature.

  8. Quench performance of Fermilab/General Dynamics built full length SSC collider dipole magnets

    SciTech Connect

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

    1992-04-01

    In this paper we present results of quench testing of full length SSC dipole magnets at Fermilab. The data are from the first six of a series of thirteen 15 m long, 50 mm aperture SSC dipole magnets which are being built and tested at Fermilab. These magnets were designed jointly by Fermilab, Brookhaven Laboratory, Lawrence Berkeley Laboratory and the SSC laboratory. Among the major goals for this series of magnets are to transfer magnet production technology to the lead vendor for the Collider Dipole Magnet, the General Dynamics Corporation, and to demonstrate industrial production by the vendor. The first magnet in the series, DCA311, was built by Fermilab technicians to establish assembly procedures. The second magnet, DCA312, was the ''technology transfer magnet'' and was built jointly by Fermilab and General Dynamics technicians. The next seven, DCA313- 319 are being built by General Dynamics personnel using Fermilab facilities and procedures. However, Fermilab personnel still operate the major tooling, provide the welders, perform assembly of items that would not be part of production magnets (e.g. voltage taps), and oversee the QA program. Five of these 7 GD-built magnets will be used in the Accelerator Systems String Test (ASST) to be carried out in Dallas later this year. The last four magnets, DCA320-323, are being built by Fermilab alone.

  9. A table top experiment to study plasma confined by a dipole magnet

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Sudeep; Baitha, Anuj Ram

    2016-10-01

    There has been a long quest to understand charged particle generation, confinement and underlying complex processes in a plasma confined by a dipole magnet. Our earth's magnetosphere is an example of such a naturally occurring system. A few laboratory experiments have been designed for such investigations, such as the Levitated Dipole Experiment (LDX) at MIT, the Terella experiment at Columbia university, and the Ring Trap-1 (RT-1) experiment at the University of Tokyo. However, these are large scale experiments, where the dipole magnetic field is created with superconducting coils, thereby, necessitating power supplies and stringent cryogenic requirements. We report a table top experiment to investigate important physical processes in a dipole plasma. A strong cylindrical permanent magnet, is employed to create the dipole field inside a vacuum chamber. The magnet is suspended and cooled by circulating chilled water. The plasma is heated by electromagnetic waves of 2.45 GHz and a second frequency in the range 6 - 11 GHz. Some of the initial results of measurements and numerical simulation of magnetic field, visual observations of the first plasma, and spatial measurements of plasma parameters will be presented.

  10. Radiative heat transfer in many-body systems: Coupled electric and magnetic dipole approach

    NASA Astrophysics Data System (ADS)

    Dong, Jian; Zhao, Junming; Liu, Linhua

    2017-03-01

    The many-body radiative heat transfer theory [P. Ben-Abdallah, S.-A. Biehs, and K. Joulain, Phys. Rev. Lett. 107, 114301 (2011), 10.1103/PhysRevLett.107.114301] considered only the contribution from the electric dipole moment. For metal particles, however, the magnetic dipole moment due to eddy current plays an important role, which can further couple with the electric dipole moment to introduce crossed terms. In this paper, we develop the coupled electric and magnetic dipole (CEMD) approach for the radiative heat transfer in a collection of objects in mutual interaction. Due to the coupled electric and magnetic interactions, four terms, namely the electric-electric, the electric-magnetic, the magnetic-electric, and the magnetic-magnetic terms, contribute to the radiative heat flux and the local energy density. The CEMD is applied to study the radiative heat transfer between various dimers of nanoparticles. It is found that each of the four terms can dominate the radiative heat transfer depending on the position and composition of particles. Moreover, near-field many-body interactions are studied by CEMD considering both dielectric and metallic nanoparticles. The near-field radiative heat flux and local energy density can be greatly increased when the particles are in coupled resonances. Surface plasmon polariton and surface phonon polariton can be coupled to enhance the radiative heat flux.

  11. 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.

  12. Magnetic dipole moment of a spherical shell with TRM acquired in a field of internal origin. [Thermoremanent Magnetization implications for lunar magnetic field

    NASA Technical Reports Server (NTRS)

    Srnka, L. J.

    1976-01-01

    The acquisition of thermoremanent magnetization (TRM) by a cooling spherical shell is studied for internal magnetizing dipole fields, using Runcorn's (1975) theorems on magnetostatics. If the shell cools progressively inward, inner regions acquire TRM in a net field composed of the dipole source term plus a uniform field due to the outer magnetized layers. In this case, the global dipole moment and external remanent field are nonzero when the whole shell has cooled below the Curie point and the source dipole has disappeared. The remanent field outside the shell is found to depend on the thickness, radii, and cooling rate of the shell, as well as the coefficient of TRM and the intensity of the magnetizing field. Some implications for the moon's remanent dipole moment are discussed.

  13. Magnetic anomaly inversion using magnetic dipole reconstruction based on the pipeline section segmentation method

    NASA Astrophysics Data System (ADS)

    Pan, Qi; Liu, De-Jun; Guo, Zhi-Yong; Fang, Hua-Feng; Feng, Mu-Qun

    2016-06-01

    In the model of a horizontal straight pipeline of finite length, the segmentation of the pipeline elements is a significant factor in the accuracy and rapidity of the forward modeling and inversion processes, but the existing pipeline segmentation method is very time-consuming. This paper proposes a section segmentation method to study the characteristics of pipeline magnetic anomalies—and the effect of model parameters on these magnetic anomalies—as a way to enhance computational performance and accelerate the convergence process of the inversion. Forward models using the piece segmentation method and section segmentation method based on magnetic dipole reconstruction (MDR) are established for comparison. The results show that the magnetic anomalies calculated by these two segmentation methods are almost the same regardless of different measuring heights and variations of the inclination and declination of the pipeline. In the optimized inversion procedure the results of the simulation data calculated by these two methods agree with the synthetic data from the original model, and the inversion accuracies of the burial depths of the two methods are approximately equal. The proposed method is more computationally efficient than the piece segmentation method—in other words, the section segmentation method can meet the requirements for precision in the detection of pipelines by magnetic anomalies and reduce the computation time of the whole process.

  14. Photophysical properties and thermochromic shifts of electronic spectra of Nile Red in selected solvents. Excited states dipole moments

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2009-05-01

    Photophysical parameters, the rate constants for radiative ( kF) and nonradiative ( kIC) for Nile Red (NR) in aprotic polar solvents incapable of hydrogen bonding with NR have been determined. No regular polarity dependence on kIC were observed in contrast to other authors. The effect of temperature on absorption and fluorescence spectra of NR in two selected solvents: ethyl acetate and 1,2-dichloroethane was studied and the electric dipole moment in the excited state S 1 was determined using the Bilot and Kawski theory [L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621, L. Bilot, A. Kawski, Z. Naturforsch. 18a (1963) 10, 256]. For the previously obtained dipole moment in the ground state μg = 8.2 D [A. Kawski, P. Bojarski, B. Kukliński, Chem. Phys. Lett. 463 (2008) 410] the change from thermochromic measurements upon excitation of NR is equal to Δ μ = μe - μg = 1.75 ± 0.5 D and is in good agreement with the value Δ μ = 1.8 ± 1 D from solvatochromic method. A comparison of the obtained Δ μ value with those of other authors is given and discussed. It has been concluded that the difference between the excited μe and ground μg state dipole moments for NR is too small to create a TICT state.

  15. Magnetic antenna excitation of whistler modes. III. Group and phase velocities of wave packets

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    The properties of whistler modes excited by single and multiple magnetic loop antennas have been investigated in a large laboratory plasma. A single loop excites a wavepacket, but an array of loops across the ambient magnetic field B0 excites approximate plane whistler modes. The single loop data are measured. The array patterns are obtained by linear superposition of experimental data shifted in space and time, which is valid in a uniform plasma and magnetic field for small amplitude waves. Phasing the array changes the angle of wave propagation. The antennas are excited by an rf tone burst whose propagating envelope and oscillations yield group and phase velocities. A single loop antenna with dipole moment across B0 excites wave packets whose topology resembles m = 1 helicon modes, but without radial boundaries. The phase surfaces are conical with propagation characteristics of Gendrin modes. The cones form near the antenna with comparable parallel and perpendicular phase velocities. A physical model for the wave excitation is given. When a wave burst is applied to a phased antenna array, the wave front propagates both along the array and into the plasma forming a "whistler wing" at the front. These laboratory observations may be relevant for excitation and detection of whistler modes in space plasmas.

  16. Electro-Magnetic Dipole Properties of The Even-Even {sup 160}Gd Nucleus in The Spectroscopic Region

    SciTech Connect

    Ertugral, Filiz; Kuliev, Ali; Guliyev, Ekber

    2008-11-11

    In this study result of calculations using rotational, translational and Galilean invariant quasiparticle random-phase approximation is presented for the low lying dipole excitations in the even-even {sup 60}Gd nucleus. To make detail structure analysis for electric and magnetic dipole states, calculations carried out for both {delta}K = 1 and {delta}K = 0 branches. The analysis shows that almost all transitions with {delta}K = 1 are magnetic character in 2.4 divide 4 MeV energy interval. However, the calculations indicate the presence of a few prominent negative parity K{sup {pi}} = 1 states in the investigated energy interval, one of them with rather high E1 strength B(E1) = 7.1{center_dot}10{sup -3} e{sup 2} fm{sup 2} at energy 3.2 MeV. Calculated M1 dipole strength of the scissors mode K{sup {pi}} = 1{sup +} excitations clustered in two groups around 2.7 and 3.3 MeV. A similar situation arises for the experimentally obtained states two bumps around {omega}{sub i} = 2.7 MeV and {omega}{sub i} = 3.3 MeV. It has been shown that main part of spin-1 states, observed at energy 2.4 divide 4 MeV in {sup 160}Gd may be attributed to have M1 character and may be interpreted as main fragments of the scissors mode. However, it is apparent that the experimental data exceeds the calculation results for the summed B(M1) by a factor of 1.13 for M1 transitions.

  17. 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.

  18. Magnetic dipole moment estimates for an ancient lunar dynamo

    NASA Technical Reports Server (NTRS)

    Anderson, K. A.

    1983-01-01

    The four measured planetary magnetic moments combined with a recent theoretical prediction for dynamo magnetic fields suggests that no dynamo exists in the moon's interior today. For the moon to have had a magnetic moment in the past of sufficient strength to account for at least some of the lunar rock magnetism, the rotation would have been about twenty times faster than it is today and the radius of the fluid, conducting core must have been about 750 km. The argument depends on the validity of the Busse solution to the validity of the MHD problem of planetary dynamos.

  19. 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.

  20. Communication: Evidence for dipole-bound excited states in gas-phase I- ṡ MI (M = Na, K, Cs) anionic salt microclusters

    NASA Astrophysics Data System (ADS)

    Harvey, Andrew J. A.; Yoshikawa, Naruo; Wang, Jin-Guo; Dessent, Caroline E. H.

    2015-09-01

    We report the first UV laser photodissociation spectra of gas-phase I- ṡ MI (M = Na, K, Cs) alkali halide anionic microclusters. The photodepletion spectra of these clusters display strong absorption bands just below the calculated vertical detachment energies, indicative of the presence of dipole-bound excited states. Photoexcitation at the peak of the transition to the dipole-bound excited state results in production of a primary [MI]- photofragment along with a less intense I- ion. The photofragmentation mechanism of the excited state cluster is discussed in the context of an initial dipole-bound excited state that subsequently relaxes via a vibrational Feschbach resonance. The experiments described have been performed in an electrospray source laser-interfaced quadrupole ion-trap instrument and demonstrated for the first time that dipole-bound excited states can be identified in the relatively high-collision environment of a quadrupole ion-trap, in particular for systems with large dipole moments associated with the presence of charge separation. This indicates considerable potential for future experiments that identify dipole-bound excited states as a "low-resolution" structural probe of biomolecules and molecular charge separation using the instrumentation employed in this work.

  1. Excited-state mixed valence in a diphenyl hydrazine cation: Spectroscopic consequences of coupling and transition dipole moment orientation.

    PubMed

    Lockard, Jenny V; Zink, Jeffrey I; Trieber Ii, Dwight A; Konradsson, Asgeir E; Weaver, Michael N; Nelsen, Stephen F

    2005-02-17

    A quantitative model of mixed-valence excited-state spectroscopy is developed and applied to 2,3-diphenyl-2,3-diazabicyclo[2.2.2]octane. The lowest-energy excited state of this molecule arises from a transition from the ground state, where the charge is located on the hydrazine bridge, to an excited state where the charge is associated with one phenyl group or the other. Coupling splits the absorption band into two components with the lower-energy component being the most intense. The sign of the coupling, derived by using a neighboring orbital model, is positive. The transition dipole moments consist of parallel and antiparallel vector components, and selection rules for each are derived. Bandwidths are caused by progressions in totally symmetric modes determined from resonance Raman spectroscopic analysis. The absorption, emission, and Raman spectra are fit simultaneously with one parameter set.

  2. The role of magnetic dipoles and non-zero-order Bragg waves in metamaterial perfect absorbers.

    PubMed

    Zeng, Yong; Chen, Hou-Tong; Dalvit, Diego A R

    2013-02-11

    We develop a simple treatment of a metamaterial perfect absorber (MPA) based on grating theory. We analytically prove that the condition of MPA requires the existence of two currents, which are nearly out of phase and have almost identical amplitude, akin to a magnetic dipole. Furthermore, we show that non-zero-order Bragg modes within the MPA may consume electromagnetic energy significantly.

  3. 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…

  4. Development of cos-theta Nb{sub 3}Sn dipole magnets for VLHC

    SciTech Connect

    Alexander Zlobin et al.

    2001-07-20

    This paper describes the double aperture dipole magnets developed for a VLHC based on Nb{sub 3}Sn superconductor, a cos-theta coil, cold and warm iron yokes, and the wind-and-react fabrication technique. Status of the model R and D program, strand and cable and other major component development are also discussed.

  5. 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.

  6. Concentration dependence of the wings of a dipole-broadened magnetic resonance line in magnetically diluted lattices

    NASA Astrophysics Data System (ADS)

    Zobov, V. E.; Kucherov, M. M.

    2017-01-01

    The singularities of the time autocorrelation functions (ACFs) of magnetically diluted spin systems with dipole-dipole interaction (DDI), which determine the high-frequency asymptotics of autocorrelation functions and the wings of a magnetic resonance line, are studied. Using the self-consistent fluctuating local field approximation, nonlinear equations are derived for autocorrelation functions averaged over the independent random arrangement of spins (magnetic atoms) in a diamagnetic lattice with different spin concentrations. The equations take into account the specificity of the dipole-dipole interaction. First, due to its axial symmetry in a strong static magnetic field, the autocorrelation functions of longitudinal and transverse spin components are described by different equations. Second, the long-range type of the dipole-dipole interaction is taken into account by separating contributions into the local field from distant and near spins. The recurrent equations are obtained for the expansion coefficients of autocorrelation functions in power series in time. From them, the numerical value of the coordinate of the nearest singularity of the autocorrelation function is found on the imaginary time axis, which is equal to the radius of convergence of these expansions. It is shown that in the strong dilution case, the logarithmic concentration dependence of the coordinate of the singularity is observed, which is caused by the presence of a cluster of near spins whose fraction is small but contribution to the modulation frequency is large. As an example a silicon crystal with different 29Si concentrations in magnetic fields directed along three crystallographic axes is considered.

  7. Fine structure of the dipole excitations of the even-even 160Gd nucleus in the spectroscopic region

    NASA Astrophysics Data System (ADS)

    Ertuğral, Filiz; Guliyev, Ekber; Kuliev, Ali; Yildirim, Zemine

    2009-12-01

    In this study, the result of calculations using rotational, translational and Galilean invariant quasiparticle random-phase approximation is presented for the low-lying dipole excitations in the even-even 160Gd nucleus. Calculations are carried out for both ΔK=1 and ΔK=0 branches. The analysis shows that the main part of spin-1 states, observed at energy 2.4-4 MeV in 160Gd, have M1 character and are interpreted as main fragments of the scissors mode. The calculations indicate the presence of a few prominent negativeparity dipole ΔK=1 states in the investigated energy region, in agreement with experiment.

  8. Determination of dipole moment in the ground and excited state by experimental and theoretical methods of N-nonyl acridine orange.

    PubMed

    Wiosetek-Reske, Agnieszka M; Wysocki, Stanisław; Bak, Grzegorz W

    2005-12-01

    The absorption and fluorescence spectra of N-nonyl acridine orange are determined at room temperature (298 K) in cyclohexane, benzene, carbon tetrachloride, chloroform, chlorobenzene and dichloromethane. The ground state of dipole moment was obtained by impedance measurements using Guggenheim-Debeye's method. The experimental excited state dipole moment of N-nonyl acridine orange was determined using Bakhshiev's and Kawski-Chamma-Viallet's formulae and solvent polarity parameter proposed by Reichardt. These experimental results were completed with theoretical results using quantum chemical methods. The experimental (muexp=10.76 D) and theoretical (mucal=9.9 D) dipole moments in the ground and excited state (muexp*=14.56 D) were compared.

  9. 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.

  10. The investigation of dipole excitations in double-even 184W nuclei at the spectroscopic energy region

    NASA Astrophysics Data System (ADS)

    Zenginerler, Zemine; Ertugral, Filiz; Guiyev, Ekber; Kuliev, Ali Ekber

    2014-03-01

    The dipole excitations of double-even nucleus 184W are studied using the QRPA model with rotational, translational and Galilean invariant Hamilonian. This approach not only gives opportunity to test for the validity of the present theory and it also allows for the interpretation of the experimentally spin unknown states. The analysis of calculation shows that M1 strength, mainly an orbital character predicted from calculations of orbit-to-spin ratio, has a relative contribution, rougly 63% with summed M1 widths ΣΓ0red (M 1) = 5 . 3meV between 2<ωi<3.7 MeV, to summed ground-state decay widths of dipole mode. The experimental summed widths in the same energy interval is ΣΓored (exp) = 4.73 +/- 1.28 meV. On the other hand, several well pronounced electric dipole K = 1 excitation in spectroscopic region where mainly fulled with M1 dipole states is predicted. The total E1 widths with K = 1 is ΣΓ0red (E 1) = 2 . 62meV (30% of the summed widths), quite close to the experimental value with K = 0 ΣΓored (exp) = 2.09 +/- 0.59 meV. The theory also indicates a few positive (ΣΓ0red (M 1) = 0 . 24meV) and negative parity ΣΓ0red (E 1) = 0 . 34meV with K = 0 states with summed widths, respectively.

  11. 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.

  12. 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.

  13. Magnetic field angle changes during manufacture and testing of SSC collider dipoles

    SciTech Connect

    Kuchnir, M.; Bleadon, M.; Delchamps, S.W.; Schmidt, E.; Bossert, R.; Carson, J.; Gourlay, S.; Hanft, R.; Koska, W.; Lamm, M.J.; Mazur, P.O.; Orris, D.; Ozelis, J.; Strait, J.; Wake, M.; Devred, A.; DiMarco, J.; Kuzminski, J.; Ogitsu, T.; Yu, Y.; Zheng, H.

    1992-10-01

    Measurements of the magnetic field angle along the length of collider dipole magnets are discussed. These superconducting magnets were built at Fermilab for the Superconducting Super Collider (SSC) by Fermilab and General Dynamics personnel. These measurements were made at four stages in the assembly and test sequence. The data show-that changes can occur both during installation in the cryostat and as a result of cold testing. Most of the changes during installation are correlated with the welding of the tie bar restraints. But the changes observed as a result of the cold testing can be attributed to changes in the magnetization of the iron laminations.

  14. 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.

  15. Electric Quadrupole and Magnetic Dipole Moments of Mirror Nuclei and Self-Conjugate Nuclei

    NASA Astrophysics Data System (ADS)

    Zickendraht, W.

    A transformation, which brings about the unification of the nuclear collective and single particle models, yields sumrules for the magnetic dipole moments and for the electric quadrupole moments of mirror nuclei. These sumrules are applied to cases, for which the numerical values of these moments are known.Translated AbstractElektrische Qadrupol- und Magnetische Dipolmomente von Spiegelkernen und Kernen mit N = ZMit Hilfe einer Transformation, die die Vereinigung von Kollektiv- und Schalenmodell liefert, lassen sich Summenregeln für die magnetischen Dipol- und die elektrischen Quadrupolmomente von Spiegelkernen ableiten. Diese Summenregeln werden auf Spiegelkerne angewandt, für die die numerischen Werte der Momente bekannt sind.

  16. Magnetic excitations in iron chalcogenide superconductors.

    PubMed

    Kotegawa, Hisashi; Fujita, Masaki

    2012-10-01

    Nuclear magnetic resonance and neutron scattering experiments in iron chalcogenide superconductors are reviewed to make a survey of the magnetic excitations in FeSe, FeSe1-x Te x and alkali-metal-doped Ax Fe2-y Se2 (A = K, Rb, Cs, etc). In FeSe, the intimate relationship between the spin fluctuations and superconductivity can be seen universally for the variations in the off-stoichiometry, the Co-substitution and applied pressure. The isovalent compound FeTe has a magnetic ordering with different wave vector from that of other Fe-based magnetic materials. The transition temperature Tc of FeSe increases with Te substitution in FeSe1-x Te x with small x, and decreases in the vicinity of the end member FeTe. The spin fluctuations are drastically modified by the Te substitution. In the vicinity of the end member FeTe, the low-energy part of the spin fluctuation is dominated by the wave vector of the ordered phase of FeTe; however, the reduction of Tc shows that it does not support superconductivity. The presence of same wave vector as that of other Fe-based superconductors in FeSe1-x Te x and the observation of the resonance mode demonstrate that FeSe1-x Te x belongs to the same group as most of other Fe-based superconductors in the entire range of x, where superconductivity is mediated by the spin fluctuations whose wave vector is the same as the nesting vector between the hole pockets and the electron pockets. On the other hand, the spin fluctuations differ for alkali-metal-doped Ax Fe2-y Se2 and FeSe or other Fe-based superconductors in their wave vector and strength in the low-energy part, most likely because of the different Fermi surfaces. The resonance mode with different wave vector suggests that Ax Fe2-y Se2 has an exceptional superconducting symmetry among Fe-based superconductors.

  17. Electromagnetic fields and currents excited by dipoles normal to the conducting surface of dielectric loaded bodies of revolution

    NASA Astrophysics Data System (ADS)

    Ozzaim, Cengiz

    1999-12-01

    A modulated laser beam incident upon a conducting surface can cause electrons to be emitted in such a way that the resulting electromagnetic radiation is closely approximated by that from a distribution of electric dipoles normal to the surface. A major goal of this research has been to develop an understanding of the coupling of electromagnetic energy from the modulated laser light to objects and to the medium surrounding the object. Specific attention is focused upon coupling of the laser-induced electromagnetic field to structures which exhibit some of the characteristics of symmetric antennas. A method is presented for computing the signal caused by a modulated laser beam at a load impedance terminating a coaxial waveguide whose center conductor protrudes into a thin-wall cylindrical tube. The tube is open at one end and, on the other, it has a planar bottom through which the coax center conductor protrudes. Two case are treated: one in which the cavity is empty (free space) and a second in which it is partially filled with a dielectric insert. The excitation is the signal radiated by electrons emitted from the conducting surface by an impinging laser beam, modulated in such a way that the electrons at the surface oscillate harmonically in time. The computations are based on a procedure involving the formulation and numerical solution of integral equations plus utilization of the reciprocity theorem. A model was fabricated and experimental data were obtained to corroborate the results obtained from theory and numerical analysis. A similar analysis was conducted to determine the axial electric field at the focal point of the common parabolic reflector antenna illuminated by the laser-induced dipoles, but no experiments were performed in this case. It has been found that for the dipole excitation, penetration and coupling results are markedly different from those expected for more traditional excitations.

  18. Excitation spectra of disordered dimer magnets near quantum criticality.

    PubMed

    Vojta, Matthias

    2013-08-30

    For coupled-dimer magnets with quenched disorder, we introduce a generalization of the bond-operator method, appropriate to describe both singlet and magnetically ordered phases. This allows for a numerical calculation of the magnetic excitations at all energies across the phase diagram, including the strongly inhomogeneous Griffiths regime near quantum criticality. We apply the method to the bilayer Heisenberg model with bond randomness and characterize both the broadening of excitations and the transfer of spectral weight induced by disorder. Inside the antiferromagnetic phase this model features the remarkable combination of sharp magnetic Bragg peaks and broad magnons, the latter arising from the tendency to localization of low-energy excitations.

  19. 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.

  20. Systematics of the Electric and Magnetic Dipole Response in N=82 Isotones Below the Neutron Separation Energy

    NASA Astrophysics Data System (ADS)

    Tonchev, A. P.; Kwan, E.; Raut, R.; Rusev, G.; Tornow, W.; Hammond, S.; Kelley, J. H.; Tsoneva, N.; Lenske, H.

    2013-03-01

    In stable and weakly bound neutron-rich nuclei, a resonance-like concentration of dipole states has been observed for excitation energies around the neutron separation energy. This clustering of strong dipole states has been named the pygmy dipole resonance in contrast to the giant dipole resonance that dominates the E1 response. Understanding the pygmy resonance is presently of great interest in nuclear structure and nuclear astrophysics. High-sensitivity studies of E1 and M1 transitions in N=82 nuclei using the quasi monoenergetic and 100% linearly-polarized photon beams from High-Intensity-Gamma-Ray Source facility is presented. The nuclear dipole-strength distribution of the pygmy resonance has been measured and novel information about the character of this mode of excitation has been obtained. The data are compared with predictions from statistical and quasiparticle random-phase approximation models.

  1. Determination of the Dipole Geometry of Fluorescent Nanoparticles Using Polarized Excitation and Emission Analysis.

    PubMed

    Li, Jianan; Kwok, Ka-Cheung; Cheung, Nai-Ho

    2016-02-01

    We demonstrate that the geometries of the absorption dipole μab and emission dipole μem of nano-emitters such as quantum dots can be determined simultaneously by far-field polarimetry. The method involves plotting the emission polarization ratio against the absorption polarization ratio of single nano-emitters. Using Monte Carlo simulation, we show that these plots depend sensitively on the aspect ratio of the dipole shape. For example, the so-called 3D-2D dipole combination, that is, μab of radius ratio 1:1:1 and μem of ratio 1:1:0, would give rise to a vertical line plot. Polarization ratios of commercial cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots are measured and plotted. The empirical data points are best-fitted to yield μab of radius ratio 1:1:0.28 and μem of ratio 1:1:0.

  2. Search for magnetic dipole strength and giant spin-flip resonances in heavy nuclei. [120 to 200 MeV

    SciTech Connect

    Horen, D J

    1980-01-01

    A description is given of the use of high-resolution (n,n) scattering and the (p,n) reaction as tools to investigate highly excited states, with emphasis on information pertaining to magnetic dipole strength and giant spin-flip resonances in heavy nuclei. It is shown how the ability to determine uniquely the spins and parities of resonances observed in neutron scattering has been instrumental to an understanding of the distribution of M1 strength in /sup 207/ /sup 208/Pb. Some recent results of (p,n) studies with intermediate energy protons are discussed. Energy systematics of the giant Gamow-Teller (GT) resonance as well as new ..delta..l = ..delta..S = 1 resonance with J/sup ..pi../ = (1,2)/sup -/ are presented. It is shown how the (p,n) reaction might be useful in locating M1 strength in heavy nuclei. 20 figures.

  3. Fabrication and component testing results for a Nb{sub 3}Sn dipole magnet

    SciTech Connect

    Dell`Orco, D.; Scanlan, R.M.; Taylor, C.E.; Lietzke, A.; Caspi, S.; van Oort, J.M.; McInturff, A.D.

    1994-10-01

    At present, the maximum field achieved in accelerator R&D dipoles is slightly over 10T, with NbTi conductor at 1.8 K. Although Nb{sub 3}Sn has the potential to achieve much higher fields, none of the previous dipoles constructed from Nb{sub 3}Sn have broken the 10T barrier. We report here on the construction of a dipole with high current density Nb{sub 3}Sn with a predicted short sample limit of 13T. A wind and react technique, followed by epoxy impregnation of the fiberglass insulated coils, was used. The problems identified with the use of Nb{sub 3}SD in earlier dipole magnets were investigated in a series of supplemental tests. This includes measurement of the degradation of J{sub c} with transverse strain, cabling degradation, joint resistance measurements, and epoxy strength tests. In addition, coff assembly techniques were developed to ensure that adequate prestress could be applied without damaging the reacted Nb{sub 3}Sn cable. We report here the results of these tests and the construction status of this 50 mm bore dipole.

  4. Electrooptical Absorption Measurements (EOAM) Testify Existence of two Conformers of Prodan and Laurdan with Different Dipole Moments in Equilibrium Ground and Franck-Condon Excited State.

    PubMed

    Nemkovich, N A; Detert, H; Roeder, N

    2016-09-01

    The results from the electrooptical absorption measurements (EOAM) on the equilibrium ground and excited Franck-Condon state dipole moments of Prodan and Laurdan in 1,4-dioxane are presented. As follows from experiments Prodan and Laurdan in the equilibrium ground and excited Franck-Condon state have two conformers with considerably different dipole moments. The electrical dipole moments and the transition dipole moment, obtained from the short-wavelength region of the absorption spectrum are parallel. The electrical dipole moments measured at the long-wavelength spectral region are parallel to each other but not parallel to the transition dipole moment m a. The angle θ between the transition dipole moment m a and the dipole moment in the equilibrium ground state μ g of the long-wavelength conformer is about 30(0) for both probes. Obtained results evidence that donor-acceptor pairs of the short-wavelength and long-wavelength conformers are not located on the same axis. Two low-energy conformers of Prodan have been found by density functional theory (DFT) calculations, differing in the orientation of the carbonyl group towards the naphthalene system.

  5. Magnetic excitations in (SiO 2)Co nano-composite films: Brillouin light scattering study

    NASA Astrophysics Data System (ADS)

    Stashkevich, A. A.; Roussigné, Y.; Stognij, A. I.; Novitskii, N. I.; Wurtz, G.; Zayats, A. V.; Viau, G.; Chaboussant, G.; Ott, F.; Lutsev, L. V.; Djemia, P.; Kostylev, M. P.; Belotelov, V.

    2009-04-01

    Behaviour of magnetic excitations in the Damon-Eshbach (DE) and backward volume (BV) geometries in nano-composite (SiO 2) 100-xCo x (50% at< x<80% at) films has been studied by Brillouin light scattering (BLS). It has been shown that it is the structure of Stokes/anti-Stokes BLS lines in the DE geometry that allows reliable identification of dipole-exchange spin waves (SW) and numerical estimation of the value of the effective exchange constant A eff of a super-ferromagnetic nano-granular sample ( x=80% at).

  6. 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.

  7. 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.

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

    PubMed

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

    2009-11-20

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

  9. Influence of excited configurations on the intensities of electric-dipole transitions of rare-earth ions

    NASA Astrophysics Data System (ADS)

    Dunina, E. B.; Kornienko, A. A.

    2014-05-01

    The theory of induced electric-dipole transitions of rare-earth ions in crystals and glasses is improved by taking into account the third-order effects of perturbation theory with respect to the energies of virtual excitations of 4 f electrons to the 5 d states. Since the energy regions of excited 4 f N - 15 d states are usually superimposed with the charge-transfer bands, the effects caused by a virtual transfer of an electron from the outer shells of ions of the surroundings (ligands) to the unfilled 4 f N shells are also considered. The Pr3+, Sm3+, and Eu3+ ions are considered as examples. It is found that some difficulties inherent in the Judd-Ofelt calculation scheme are successfully overcome. The agreement of the calculated results with the experimental data improves.

  10. Mercury intrinsic magnetic field : Limits of the offset-dipole representation

    NASA Astrophysics Data System (ADS)

    Chanteur, Gérard M.; Modolo, Ronan; Richer, Emilie; Hess, Sébastien; Leblanc, François

    2013-04-01

    The interaction of the solar wind (SW) with the magnetic field of The analysis of MESSENGER orbital observations led Anderson et al (2011) to propose a dipole centered on the spin axis of the planet with a northward offset equal to 484±11 km to represent the intrinsic magnetic field of Mercury at northern latitudes higher than 30°. The magnetic moment has a magnitude of 195±10nT, points southward and is tilted by less than 3° with respect to the spin axis. The restriction to northern latitude comes from the lack of low altitude measurements of the magnetic field at southern latitudes due to MESSENGER orbit. Hence for the moment being there is no observation to constrain the representation of the southern planetary field. The suggested offset is equal to about 20% of the planetary radius which is quite a large value by comparison to 8.5% in the terrestrial case although with a lateral offset. This representation of the intrinsic field by an offset dipole suggests that the southern polar cap should be much wider than the northern one, leading to important consequences for magnetospheric dynamics. Nevertheless the offset dipole is just a convenient representation that can be fitted by the first terms of the multipolar development. The surface field of the planet produced by the offset dipole (OD) proposed by Anderson et al (2011) is thus fitted by the sum of a dipolar and a quadrupolar field (DQ) for northern latitudes higher than 50°. The resulting field differs slightly from the offset dipole field at northern latitudes but a separatrix exists at southern latitudes between dipolar-like and quadrupolar like field lines. This separatrix begins on the polar axis at an altitude RS equal to three times the ratio of the quadrupolar to the dipolar moment. When the relative axial offset of the dipole becomes larger than 16% then RS becomes larger than the planetary radius leading to important topological changes of the southern field. Global hybrid simulations of the

  11. Solvent effect on the absorption and fluorescence spectra of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin: determination of ground and excited state dipole moments.

    PubMed

    Gülseven Sıdır, Yadigar; Sıdır, Isa

    2013-02-01

    The ground state (μ(g)) and excited state (μ(e)) dipole moments of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin (abbreviated as 7ADDC) are estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (ε) and refractive index (n). While the ground state dipole moment is determined by using Bilot-Kawski method, the excited state dipole moment is calculated by using Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet and Reichardt correlation methods. Excited state dipole moment is observed as larger than the ground state dipole moment due to substantial π-electron density redistribution. The ground state and excited state dipole moments are observed as parallel to each other with angle of 0°. Solute-solvent interactions are analyzed by means of linear solvation free energy relationships (LSER) using dielectric constant function (f(ε)), refractive index function (f(n)) and Kamlet-Taft parameters (α and β). Atomic charges, electron densities and molecular orbitals are calculated in vacuum and with solvent effect by using both DFT and TDDFT methods. Solvent accessible surface, molecular electrostatic potential (MEP) and electrostatic potential (ESP) are visualized as a result of DFT calculations.

  12. Solvent effect on the absorption and fluorescence spectra of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin: Determination of ground and excited state dipole moments

    NASA Astrophysics Data System (ADS)

    Gülseven Sıdır, Yadigar; Sıdır, İsa

    2013-02-01

    The ground state (μg) and excited state (μe) dipole moments of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin (abbreviated as 7ADDC) are estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (ɛ) and refractive index (n). While the ground state dipole moment is determined by using Bilot-Kawski method, the excited state dipole moment is calculated by using Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet and Reichardt correlation methods. Excited state dipole moment is observed as larger than the ground state dipole moment due to substantial π-electron density redistribution. The ground state and excited state dipole moments are observed as parallel to each other with angle of 0°. Solute-solvent interactions are analyzed by means of linear solvation free energy relationships (LSER) using dielectric constant function (f(ɛ)), refractive index function (f(n)) and Kamlet-Taft parameters (α and β). Atomic charges, electron densities and molecular orbitals are calculated in vacuum and with solvent effect by using both DFT and TDDFT methods. Solvent accessible surface, molecular electrostatic potential (MEP) and electrostatic potential (ESP) are visualized as a result of DFT calculations.

  13. Nonlinear spin-wave excitations at low magnetic bias fields

    PubMed Central

    Bauer, Hans G.; Majchrak, Peter; Kachel, Torsten; Back, Christian H.; Woltersdorf, Georg

    2015-01-01

    Nonlinear magnetization dynamics is essential for the operation of numerous spintronic devices ranging from magnetic memory to spin torque microwave generators. Examples are microwave-assisted switching of magnetic structures and the generation of spin currents at low bias fields by high-amplitude ferromagnetic resonance. Here we use X-ray magnetic circular dichroism to determine the number density of excited magnons in magnetically soft Ni80Fe20 thin films. Our data show that the common model of nonlinear ferromagnetic resonance is not adequate for the description of the nonlinear behaviour in the low magnetic field limit. Here we derive a model of parametric spin-wave excitation, which correctly predicts nonlinear threshold amplitudes and decay rates at high and at low magnetic bias fields. In fact, a series of critical spin-wave modes with fast oscillations of the amplitude and phase is found, generalizing the theory of parametric spin-wave excitation to large modulation amplitudes. PMID:26374256

  14. Lepton electric and magnetic dipole moments via lepton flavor-violating spin-1 unparticle interactions

    SciTech Connect

    Moyotl, A.; Rosado, A.; Tavares-Velasco, G.

    2011-10-01

    The magnetic dipole moment and the electric dipole moment of leptons are calculated under the assumption of lepton flavor violation (LFV) induced by spin-1 unparticles with both vector and axial-vector couplings to leptons, including a CP-violating phase. The experimental limits on the muon magnetic dipole moment and LFV process, such as the decay l{sub i}{sup -}{yields}l{sub j}{sup -}l{sub k}{sup -}l{sub k}{sup +}, are then used to constrain the LFV couplings for particular values of the unparticle operator dimension d{sub U} and the unparticle scale {Lambda}{sub U}, assuming that LFV transitions between the tau and muon leptons are dominant. It is found that the current experimental constraints favor a scenario with dominance of the vector couplings over the axial-vector couplings. We also obtain estimates for the electric dipole moments of the electron and the muon, which are well below the experimental values.

  15. 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.

  16. Long-wavelength magnetic excitations in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Talbayev, D.; Gigax, J. G.; Taylor, A. J.; Lee, Seongsu; Cheong, S.-W.

    2009-03-01

    Magnetic and lattice vibrations play a central role in the properties of multiferroics. This low-energy electrodynamics can help unravel the fundamental interactions between magnetic and lattice degrees of freedom. BiFeO3 is a multiferroic material with robust room temperature ferroelectricity and antiferromagnetism and promising technological potential. The interaction between the ferroelectric and antiferromagnetic order parameters leads to the modification of the isotropic Heisenberg-antiferromagnet ground state that becomes an incommensurate cycloid with a very long period. The cycloidal magnetic structure results in a complex spectrum of zero-wavevector magnetic excitations; these magnetic modes were detected using Raman scattering. Here, we report a far-infrared spectroscopic study of a BiFeO3 single crystal. We detected magnetic resonances at energies close to those reported in the Raman spectroscopy studies. The magnetic character of these excitations is supported by their characteristic temperature dependence. We will discuss our results in the context of possible electric-dipole activity of the observed resonances.

  17. Simulation Analysis of a Strip Dipole Excited Electromagnetic Band-Gap (EBG) Structure

    DTIC Science & Technology

    2015-07-01

    Samii (2003). The normalization process is fairly straight forward. An observational plane is placed at a distance of 0.5λ12GHz away from the EBG...starting the design process , and comparing the 2 numerical methods is to determine which one is preferred for analyzing an EBG for antenna applications...dipoles were shortened too much in the scaling process , although from the resistance and reactance, the overcompensation was not large (Fig. 50a and b

  18. Presence of magnetic excitations in SmFeAsO

    NASA Astrophysics Data System (ADS)

    Pelliciari, Jonathan; Dantz, Marcus; Huang, Yaobo; Strocov, Vladimir N.; Xing, Lingyi; Wang, Xiancheng; Jin, Changqing; Schmitt, Thorsten

    2016-09-01

    We measured dispersive spin excitations in SmFeAsO, a parent compound of SmFeAsO1 -xFx and one of the highest temperature superconductors of Fe pnictides (TC ≈ 55 K). We determine the magnetic excitations to disperse with a bandwidth energy of ca 170 meV at (0.47, 0) and (0.34, 0.34), which merges into the elastic line approaching the Γ point. Comparing our results with other parent Fe pnictides, we show the importance of structural parameters for the magnetic excitation spectrum, with small modifications of the tetrahedron angles and As height strongly affecting the magnetism.

  19. Simulation and Characterization of the MINER{nu}A Dipole Magnets

    SciTech Connect

    Felix, J.; Castorena, J.; Higuera, A.; Urrutia, Z.; Zavala, G.

    2009-12-17

    The MINER{nu}A (Main INjector ExpeRiment for {nu} A) experiment (http://minerva.fnal.gov/) is a neutrino scattering experiment which uses the NuMI beamline at Fermilab. It seeks to measure low energy neutrino interactions both to support neutrino oscillation experiments and to study the strong dynamics of the nucleon and nucleus that affect these interactions. For energy calibration of the main detector, a tertiary test beam line was designed and commissioned. This test beam consisted of target, collimator, two TOF stations and four wire chamber stations. Two dipole trim magnets were used to form a spectrometer. Here we present the simulation and characterization of these dipole magnets.

  20. Testing the axial dipole hypothesis for the Moon by modeling the direction of crustal magnetization

    NASA Astrophysics Data System (ADS)

    Oliveira, J. S.; Wieczorek, M. A.

    2017-02-01

    Orbital magnetic field data show that portions of the Moon's crust are strongly magnetized, and paleomagnetic data of lunar samples suggest that Earth strength magnetic fields could have existed during the first several hundred million years of lunar history. The origin of the fields that magnetized the crust are not understood and could be the result of either a long-lived core-generated dynamo or transient fields associated with large impact events. Core dynamo models usually predict that the field would be predominantly dipolar, with the dipole axis aligned with the rotation axis. We test this hypothesis by modeling the direction of crustal magnetization using a global magnetic field model of the Moon derived from Lunar Prospector and Kaguya magnetometer data. We make use of a model that assumes that the crust is unidirectionally magnetized. The intensity of magnetization can vary with the crust, and the best fitting direction of magnetization is obtained from a nonnegative least squares inversion. From the best fitting magnetization direction we obtain the corresponding north magnetic pole predicted by an internal dipolar field. Some of the obtained paleopoles are associated with the current geographic poles, while other well-constrained anomalies have paleopoles at equatorial latitudes, preferentially at 90° east and west longitudes. One plausible hypothesis for this distribution of paleopoles is that the Moon possessed a long-lived dipolar field but that the dipole was not aligned with the rotation axis as a result of large-scale heat flow heterogeneities at the core-mantle boundary.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Final Assembly and Factory Testing of the Jefferson Lab SHMS Spectrometer Quadrupole and Dipole Superconducting Magnets

    DOE PAGES

    Brindza, Paul; Lassiter, Steven; Sun, Eric; ...

    2017-06-01

    Jefferson Lab is constructing an 11 Gev/c electron spectrometer called the Super High Momentum Spectrometer (SHMS) as part of the 12 GeV JLAB upgrade for experimental Hall C. Three of the five superconducting(SC) SHMS magnets are under construction at SigmaPhi in Vannes France as a result of an international competition for design and fabrication. The three magnets Q2 and Q3 60 cm bore quadrupoles and the 60 cm warm bore dipole are complete or near complete and have many design features in common. All three magnets share a common superconductor, collaring system, cryostat design, cold to warm support, cryogenic interface,more » burnout resistant current leads, DC power supply, quench protection, instrumentation and controls. The three magnets are collared, installed in cryostats and welded up and in various stages of final testing. The Q2 quadrupole is due to ship from France to America in August arriving during this ASC conference and has passed all final hipot, leak and pressure tests. The dipole is in leak and pressure testing as of July 2016 while the Q3 quadrupole requires some outer vacuum vessel assembly. Delivery of the Q3 and Dipole magnets will follow the Q2 at about 1 month intervals. Lastly, factory testing have included hipot and electrical tests, magnetic tests at low field, mechanical alignments to center the coils, leak tests and ASME Code required pressure tests. Upon installation in Hall C at JLAB cold testing will commence.« less

  6. A 50 Hz dipole magnet for the TRIUMF KAON Factory booster ring

    SciTech Connect

    Otter, A.J. )

    1992-01-01

    The 3 GeV Booster synchrotron for TRIUMF's KAON Factory will need 24 dipole magnets each 3.0 m long operating with a resonant power system designed to give a 50 Hz ac field superimposed onto a dc field. The maximum and minimum field levels are 1.118 and 0.295 T respectively. In this paper the magnet design is presented and compared with measured results from a prototype which was constructed to evaluate fabrication procedures and to verify the ac loss calculations. The experiences gained from this fabrication are described.

  7. Measurements of the persistent current decay and snapback effect in Tevatron dipole magnets

    SciTech Connect

    Velev, G.V.; Bauer, P.; DiMarco, J.; Hanft, R.; Lamm, M.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Tompkins, J.C.; /Fermilab

    2006-08-01

    A systematic study of the persistent current decay and snapback effect in the fields of Tevatron accelerator dipoles was performed at the Fermilab Magnet Test Facility (MTF). The decay and snapback were measured under a range of conditions including variations of the current ramp parameters and magnet operational history. The study has mostly focused on the dynamic behavior of the normal sextupole component. In addition, the paper presents the persistent current effects observed in the other allowed field harmonics as well. The results provide new information about the previously observed ''excess'' decay during the first several seconds of the sextupole decay during injection and the correlation between the snapback amplitude and its duration.

  8. Quantitative treatment of the effect of solvent on the electronic absorption and fluorescence spectra of substituted coumarins: Evaluation of the first excited singlet-state dipole moments.

    PubMed

    Aaron, J J; Buna, M; Parkanyi, C; Antonious, M S; Tine, A; Cisse, L

    1995-12-01

    The electronic absorption and fluorescence spectra of coumarin and 11 substituted coumarins were measured in several solvents (dioxane, ethyl ether, ethyl acetate, ethanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide). Ground-state dipole moments were determined in dioxane at 298 K. The results were used to obtain the first excited singlet-state dipole moments of the coumarins under study by the solvatochromic shift method (Bakhshiev, Kawski-Chamma-Viallet, McRae, and Suppan correlations). Also, the ground- and the first excited singlet-state dipole moments were calculated using a combination of the PPP method (π-contribution) and the vector sum of the σ-bond and group moments (σ-contribution). In general, the first excited singlet-state dipole moments of the coumarins are noticeably higher than the corresponding ground-state values, indicating a substantial redistribution of theπ-electron densities resulting in a more polar excited state. There is a reasonably good agreement between the calculated and the experimental dipole moments.

  9. Electromagnetic toroidal excitations in matter and free space.

    PubMed

    Papasimakis, N; Fedotov, V A; Savinov, V; Raybould, T A; Zheludev, N I

    2016-03-01

    The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.

  10. Electromagnetic toroidal excitations in matter and free space

    NASA Astrophysics Data System (ADS)

    Papasimakis, N.; Fedotov, V. A.; Savinov, V.; Raybould, T. A.; Zheludev, N. I.

    2016-03-01

    The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.

  11. 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.

  12. 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.

  13. Design and test of the benches for the magnetic measurement of the LHC dipoles

    NASA Astrophysics Data System (ADS)

    Billan, J.; Buckley, J.; Saban, R.; Sievers, P.; Walckiers, L.

    1994-07-01

    The magnetic measurement of more than 1300 LHC dipoles comprises the content of higher harmonic field components, field direction and field integrals. The measurements will be carried out along a warm bore installed inside the magnet cold bore, thus allowing the use of rotating coils at room temperature. This coil, together with Hall and NMR detectors is mounted at one end of a 12.5 m long shaft which is specially designed for very high rotational stiffness and which is controlled from its far end by a motor, an angular encoder and a level meter, all standard components placed outside the magnetic field without space restrictions. Particular emphasis has been put on the user-friendliness of the bench and its automated, computer-controlled operation requiring a minimum of staff, an important issue during production measurements of large series of magnets. The bench and its performance and precision achieved during its commissioning are described.

  14. Self-organized confinement by magnetic dipole: recent results from RT-1 and theoretical modeling

    NASA Astrophysics Data System (ADS)

    Yoshida, Z.; Saitoh, H.; Yano, Y.; Mikami, H.; Kasaoka, N.; Sakamoto, W.; Morikawa, J.; Furukawa, M.; Mahajan, S. M.

    2013-01-01

    Inhomogeneous magnetic field gives rise to interesting properties of plasmas which are degenerate in homogeneous (or zero) magnetic fields. Magnetospheric plasmas, as observed commonly in the Universe, are the most simple, natural realization of strongly inhomogeneous structures created spontaneously in the vicinity of magnetic dipoles. The RT-1 device produces a ‘laboratory magnetosphere’ by which stable confinement (particle and energy confinement times ˜0.5 s) of high-β (local electron β ˜ 0.7 electron temperature ≳10 keV) plasma is achieved. By producing a pure-electron plasma, we obtain clear-cut evidence of inward (or up-hill) diffusion of particles. A statistical mechanical model reveals the ‘distortion’ of phase space, induced by the inhomogeneity of the ambient magnetic field, on which the plasma relaxes into an equilibrium with inhomogeneous density while it maximizes the entropy.

  15. Excited S 1 state dipole moments of nitrobenzene and p-nitroaniline from thermochromic effect on electronic absorption spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-11-01

    The effect of temperature on the absorption spectra of nitrobenzene (NB) and p-nitroaniline (NA) in 1,2-dichloroethane was studied for temperature ranging from 295 K to 378 K and from 296 K to 408 K, respectively. With temperature increase the absorption bands of both compounds are blue shifted, which is caused by the decrease of permittivity ɛ and refractive index n. From the band shifts and by using the Bilot and Kawski theory [ L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621] the dipole moments in the excited singlet state μe = 6.59 D of NB and μe = 13.35 D of NA were determined. The influence of polarizability α, the Onsager cavity radius a and dipole moment in the ground state μg on the determined values of μe are discussed. A comparison of the obtained μe values with those of other authors is given. In the case of p-NA a strong intramolecular charge transfer (ICT) was confirmed.

  16. Excited state dipole moments of N, N-dimethylaniline from thermochromic effect on electronic absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-01-01

    The effect of temperature on absorption and fluorescence spectra of N, N-dimethylaniline (DMA) in ethyl acetate has been studied for temperature ranging from 293 to 388 K. The permittivity ɛ and refractive index n of the solvent decrease with temperature increase and the absorption and fluorescence bands are blue shifted (so-called "thermochromic shift"). Based on this phenomenon, the dipole moment μe in the excited singlet state and the Onsager interaction radius a for DMA were determined using the Bilot and Kawski theory [L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621; 18a (1963) 10, 256]. For the known dipole moment in the ground state μg = 1.61 D and for α/ a3 = 0.54 ( α is the polarizability of the solute) the average value of μe = 3.55 D and a = 3.1 Å were determined. The obtained values for DMA are compared with the experimental values determined by other authors.

  17. Estimation of ground- and excited-state dipole moments of oxazine 1 in liquid and liquid crystalline media.

    PubMed

    Gilani, A Ghanadzadeh; Moghadam, M; Zakerhamidi, M S

    2011-06-01

    The absorption and fluorescence spectra of a laser dye, oxazine-1 (OX1), in liquid and liquid crystalline media were studied at room temperature. The solvatochromic method was used to determine the ground- and excited-state dipole moments by means of Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet polarity functions. The solvent polarity has no large and regular effect on the spectral behavior of OX1, and thus it might be considered as a poor solvatochromic indicator dye. In addition, applicability of solvatochromic method for this dye in anisotropic media was investigated. On the other hand, nature and degree of the solute-solvent interactions were characterized using correlation of multi-parameter solvent polarity scales. Due to the theoretical restrictions and the dye molecular structure, deviations from the solvatochromic correlation were observed.

  18. Estimation of ground- and excited-state dipole moments of oxazine 1 in liquid and liquid crystalline media

    NASA Astrophysics Data System (ADS)

    Ghanadzadeh Gilani, A.; Moghadam, M.; Zakerhamidi, M. S.

    2011-06-01

    The absorption and fluorescence spectra of a laser dye, oxazine-1 (OX1), in liquid and liquid crystalline media were studied at room temperature. The solvatochromic method was used to determine the ground- and excited-state dipole moments by means of Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet polarity functions. The solvent polarity has no large and regular effect on the spectral behavior of OX1, and thus it might be considered as a poor solvatochromic indicator dye. In addition, applicability of solvatochromic method for this dye in anisotropic media was investigated. On the other hand, nature and degree of the solute-solvent interactions were characterized using correlation of multi-parameter solvent polarity scales. Due to the theoretical restrictions and the dye molecular structure, deviations from the solvatochromic correlation were observed.

  19. 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

  20. Simultaneous Excitation and Analysis of Three Instabilities in Magnetized Plasma

    SciTech Connect

    Dimitriu, D. G.; Ionita, C.; Schrittwieser, R. W.

    2008-03-19

    Experimental results are presented on the simultaneous excitation of three low-frequency instabilities in the magnetized plasma column of a Q-machine, namely the potential relaxation instability, the electrostatic ion-cyclotron instability and the Kelvin-Helmholtz instability. The influence of the magnetic field intensity on the appearance of these instabilities was investigated.

  1. Magnetic dipole transitions in 4d{sup N} configurations of tungsten ions

    SciTech Connect

    Jonauskas, V.; Kisielius, R.; Kyniene, A.; Kucas, S.; Norrington, P. H.

    2010-01-15

    Magnetic dipole transitions between the levels of ground 4d{sup N} configurations of tungsten ions were analyzed by employing a large basis of interacting configurations. Previously introduced configuration interaction strength between two configurations was used to determine the configurations with the largest contribution to wave functions of atomic states for the considered configurations. Collisional-radiative modeling was performed for the levels of the ground configuration coupled through electric dipole transitions with 4p{sup 5}4d{sup N+1} and 4d{sup N-1}4f configurations. New identification of some lines observed in the electron-beam ion trap plasma was proposed based on calculations in which wavelength convergence was reached.

  2. Driving magnetic order in a manganite by ultrafast lattice excitation.

    SciTech Connect

    Forst, M.; Tobey, R. I.; Wall, S.; Bromberger, H.; Khanna, V.; Cavalieri, A. L.; Chuang, Y.-D.; Lee, W. S.; Moore, R.; Schlotter, W. F.; Turner, J. J.; Krupin, O.; Trigo, M.; Zheng, H.; Mitchell, J. F.; Dhesi, S. S.; Hill, J. P.; Cavalleri, A.

    2011-01-01

    Femtosecond midinfrared pulses are used to directly excite the lattice of the single-layer manganite La{sub 0.5}Sr{sub 1.5}MnO{sub 4}. Magnetic and orbital orders, as measured by femtosecond resonant soft x-ray diffraction with an x-ray free-electron laser, are reduced within a few picoseconds. This effect is interpreted as a displacive exchange quench, a prompt shift in the equilibrium value of the magnetic- and orbital-order parameters after the lattice has been distorted. Control of magnetism through ultrafast lattice excitation may be of use for high-speed optomagnetism.

  3. Parametric Resonance of Magnetization Excited by Electric Field.

    PubMed

    Chen, Yu-Jin; Lee, Han Kyu; Verba, Roman; Katine, Jordan A; Barsukov, Igor; Tiberkevich, Vasil; Xiao, John Q; Slavin, Andrei N; Krivorotov, Ilya N

    2017-01-11

    Manipulation of magnetization by electric field is a central goal of spintronics because it enables energy-efficient operation of spin-based devices. Spin wave devices are promising candidates for low-power information processing, but a method for energy-efficient excitation of short-wavelength spin waves has been lacking. Here we show that spin waves in nanoscale magnetic tunnel junctions can be generated via parametric resonance induced by electric field. Parametric excitation of magnetization is a versatile method of short-wavelength spin wave generation, and thus, our results pave the way toward energy-efficient nanomagnonic devices.

  4. Estimation of the ground and the first excited singlet-state dipole moments of 1,4-disubstituted anthraquinone dyes by the solvatochromic method.

    PubMed

    Siddlingeshwar, B; Hanagodimath, S M

    2010-04-01

    The both, ground-state (mu(g)) and the excited-state (mu(e)) dipole moments of three 1,4-disubstituted anthraquinones, namely 1,4-diaminoanthracene-9,10-dione (1,4-DAAQ), 1-amino-4-hydroxyanthracene-9,10-dione (1,4-AHAQ), and 1,4-dihydroxyanthracene-9,10-dione (1,4-DHAQ) were estimated in binary solvent mixtures (methylcyclohexane-ethyl acetate and ethyl acetate-acetonitrile). The dipole moments (mu(g) and mu(e)) were estimated from Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet, McRae, and Suppan equations by using the variation of Stokes shift with the solvent's relative permittivity and refractive index. The ground-state dipole moments were also calculated theoretically by Gaussian 03 software using B3LYP/6-31 G* level of theory. Further, the change in dipole moment values Deltamu were also calculated by using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter (E(T)(N)). The excited-state dipole moments observed are larger than their ground-state counterparts, indicating a substantial redistribution of the pi-electron densities in a more polar excited state for all the molecules investigated.

  5. Estimation of the ground and the first excited singlet-state dipole moments of 1,4-disubstituted anthraquinone dyes by the solvatochromic method

    NASA Astrophysics Data System (ADS)

    Siddlingeshwar, B.; Hanagodimath, S. M.

    2010-04-01

    The both, ground-state ( μg) and the excited-state ( μe) dipole moments of three 1,4-disubstituted anthraquinones, namely 1,4-diaminoanthracene-9,10-dione (1,4-DAAQ), 1-amino-4-hydroxyanthracene-9,10-dione (1,4-AHAQ), and 1,4-dihydroxyanthracene-9,10-dione (1,4-DHAQ) were estimated in binary solvent mixtures (methylcyclohexane-ethyl acetate and ethyl acetate-acetonitrile). The dipole moments ( μg and μe) were estimated from Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet, McRae, and Suppan equations by using the variation of Stokes shift with the solvent's relative permittivity and refractive index. The ground-state dipole moments were also calculated theoretically by Gaussian 03 software using B3LYP/6-31 G* level of theory. Further, the change in dipole moment values Δ μ were also calculated by using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter (ETN). The excited-state dipole moments observed are larger than their ground-state counterparts, indicating a substantial redistribution of the π-electron densities in a more polar excited state for all the molecules investigated.

  6. Impact of magnetic fluctuations on lattice excitations in fcc nickel.

    PubMed

    Körmann, Fritz; Ma, Pui-Wai; Dudarev, Sergei L; Neugebauer, Jörg

    2016-02-24

    The spin-space averaging formalism is applied to compute atomic forces and phonon spectra for magnetically excited states of fcc nickel. Transverse and longitudinal magnetic fluctuations are taken into account by a combination of magnetic special quasi random structures and constrained spin-density-functional theory. It turns out that for fcc Ni interatomic force constants and phonon spectra are almost unaffected by both kinds of spin fluctuations. Given the computational expense to simulate coupled magnetic and atomic fluctuations, this insight facilitates computational modeling of magnetic alloys such as Ni-based superalloys.

  7. The magnetic toroidal dipole in steric metamaterial for permittivity sensor application

    NASA Astrophysics Data System (ADS)

    Ye, Q. W.; Guo, L. Y.; Li, M. H.; Liu, Y.; Xiao, B. X.; Yang, H. L.

    2013-11-01

    A new kind of metamaterial composed of metallic split-ring structure arranged in a two-dimensional array is designed, which shows the multipoles' resonances, especially the magnetic toroidal dipolar (MTD) resonance. The calculated scattering power proves that the resonance at 14.416 GHz is mainly excited by MTD response. Compared with the other two resonances excited by normal multipoles, MTD response has the strongest dependence on permittivity of substrate and background material, which has potential applications on permittivity sensor.

  8. 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

  9. Determination of dipole moment in the ground and excited state by experimental and theoretical methods of N-nonyl acridine orange

    NASA Astrophysics Data System (ADS)

    Wiosetek-Reske, Agnieszka M.; Wysocki, Stanisław; Bąk, Grzegorz W.

    2005-12-01

    The absorption and fluorescence spectra of N-nonyl acridine orange are determined at room temperature (298 K) in cyclohexane, benzene, carbon tetrachloride, chloroform, chlorobenzene and dichloromethane. The ground state of dipole moment was obtained by impedance measurements using Guggenheim-Debeye's method. The experimental excited state dipole moment of N-nonyl acridine orange was determined using Bakhshiev's and Kawski-Chamma-Viallet's formulae and solvent polarity parameter proposed by Reichardt. These experimental results were completed with theoretical results using quantum chemical methods. The experimental ( μexp = 10.76 D) and theoretical ( μcal = 9.9 D) dipole moments in the ground and excited state ( μexp*=14.56 D) were compared.

  10. Magnetic field component demonstration for a neutron electric dipole moment search

    NASA Astrophysics Data System (ADS)

    Slutsky, Simon

    2016-09-01

    A neutron electric dipole moment (EDM) search at the Oak Ridge National Laboratory's Spallation Neutron Source (SNS) will probe with a sensitivity of < 5 ×10-28 e-cm. Trapped, polarized ultracold neutrons will precess in a constant magnetic field and variable electric field, and a non-zero neutron EDM will appear as a variation in the precession frequency correlated with the electric field. Magnetic field gradients must be kept below 10 pT/cm to mitigate false EDMs produced by the geometric phase effect and to maximize the neutron spin-relaxation lifetime. I will discuss a prototype magnetic shielding system, including a nearly-hermetic superconducting lead shield, built to demonstrate the required gradients at 1/3-scale of the final experiment. Additionally, the system will evaluate the eddy current heating due to RF fields produced by a proposed neutron-``spin-dressing'' technique.

  11. Spin dephasing in a magnetic dipole field around large capillaries: Approximative and exact results.

    PubMed

    Kurz, F T; Buschle, L R; Kampf, T; Zhang, K; Schlemmer, H P; Heiland, S; Bendszus, M; Ziener, C H

    2016-12-01

    We present an analytical solution of the Bloch-Torrey equation for local spin dephasing in the magnetic dipole field around a capillary and for ensembles of capillaries, and adapt this solution for the study of spin dephasing around large capillaries. In addition, we provide a rigorous mathematical derivation of the slow diffusion approximation for the spin-bearing particles that is used in this regime. We further show that, in analogy to the local magnetization, the transverse magnetization of one MR imaging voxel in the regime of static dephasing (where diffusion effects are not considered) is merely the first term of a series expansion that constitutes the signal in the slow diffusion approximation. Theoretical results are in agreement with experimental data for capillaries in rat muscle at 7T.

  12. Spin dephasing in a magnetic dipole field around large capillaries: Approximative and exact results

    NASA Astrophysics Data System (ADS)

    Kurz, F. T.; Buschle, L. R.; Kampf, T.; Zhang, K.; Schlemmer, H. P.; Heiland, S.; Bendszus, M.; Ziener, C. H.

    2016-12-01

    We present an analytical solution of the Bloch-Torrey equation for local spin dephasing in the magnetic dipole field around a capillary and for ensembles of capillaries, and adapt this solution for the study of spin dephasing around large capillaries. In addition, we provide a rigorous mathematical derivation of the slow diffusion approximation for the spin-bearing particles that is used in this regime. We further show that, in analogy to the local magnetization, the transverse magnetization of one MR imaging voxel in the regime of static dephasing (where diffusion effects are not considered) is merely the first term of a series expansion that constitutes the signal in the slow diffusion approximation. Theoretical results are in agreement with experimental data for capillaries in rat muscle at 7 T.

  13. 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.

  14. 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.

  15. Quantitative treatment of the solvent effects on the electronic absorption and fluorescence spectra of acridines and phenazines. The ground and first excited singlet-state dipole moments

    NASA Astrophysics Data System (ADS)

    Aaron, Jean Jacques; Maafi, Mounir; Párkányi, Cyril; Boniface, Christian

    1995-04-01

    Electronic absorption and fluorescence excitation and emission spectra of four acridines (acridine, Acridine Yellow, 9-aminoacridine and proflavine) and three phenazines (phenazine, neutral Red and safranine) are determined at room temperature (298 K) in several solvents of various polarities (dioxane, chloroform, ethyl ether, ethyl acetate, 1-butanol, 2-propanol, ethanol, methanol, dimethylformamide, acetonitrile and dimethyl sulfoxide). The effect of the solvent upon the spectral characteristics of the above compounds, is studied. In combination with the ground-state dipole moments of these compounds, the spectral data are used to evaluate their first excited singlet-state dipole moments by means of the solvatochromic shift method (Bakhshiev's and Kawski-Chamma-Viallet's correlations). The theoretical ground and excited singlet-state dipole moments for acridines and phenazines are also calculated as a vector sum of the π-component (obtained by the PPP method) and the σ-component (obtained from σ-bond moments). For most acridines and phenazines under study, the experimental excited singlet-state dipole moments are found to be higher than their ground state counterpart. The application of the Kamlet-Abboud-Taft solvatochromic parameters to the solvent effect on spectral properties of acridine and phenazine derivatives is discussed.

  16. The dependence of the coupled magnetosphere-ionosphere-thermosphere system on the Earth's magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Cnossen, Ingrid; Richmond, Arthur D.; Wiltberger, Michael

    2012-05-01

    The strength of the Earth's magnetic field changes over time. We use simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere model to investigate how the magnetosphere, upper atmosphere, and solar quiet (Sq) geomagnetic variation respond as the geomagnetic dipole moment M varies between 2ṡ1022 and 10ṡ1022 Am2. We find that the magnetopause stand-off distance and the cross-polar cap potential increase, while the polar cap size decreases, with increasing M. Their dependence on M is stronger than predicted by previous studies. We also show for the first time that the shape of the magnetosphere starts to change for M ≤ 4ṡ1022 Am2. This may be due to enhanced magnetopause erosion and/or to strong changes in the ionospheric conductance, which affect the field-aligned currents and the magnetic fields they create in the magnetosphere, thus modifying the magnetic pressure inside the magnetosphere. E × B drift velocities, Joule heating power, the global mean thermospheric temperature and the global mean height of the peak of the ionospheric F2 layer, hmF2, all increase with increasing M for low dipole moments, but all decrease with increasing M for larger dipole moments. The peak electron density of the F2 layer, NmF2, shows the opposite behavior. The Sq amplitude decreases with increasing M and this dependence can be roughly described by a power law scaling. Most scaling relations show a weak dependence on the solar activity level, which is likely associated with a change in the relative contributions to the Pedersen conductance from the upper and lower ionosphere, which scale differently with M.

  17. Magnetic and quasiparticle excitations in cuprates

    NASA Astrophysics Data System (ADS)

    Bennemann, K.-H.

    2005-09-01

    [Dedicated to Bernhard Mühlschlegel on the occasion ofhis 80th birthday]Assuming for simplicity that the electrons or the holes in cuprate superconductors interact predominantly with spin-fluctuations, we determine within the random phase approximation (RPA)the dynamical susceptibility, in particular the resonance peak resulting as feedback from superconductivity, as well as the elementary quasiparticle excitations in hole-doped systems.

  18. 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.

  19. Influence of spin-orbit coupling on the magnetic dipole term Tα

    NASA Astrophysics Data System (ADS)

    Šipr, O.; Minár, J.; Ebert, H.

    2016-10-01

    The influence of the spin-orbit coupling (SOC) on the magnetic dipole term Tα is studied across a range of systems in order to check whether the Tα term can be eliminated from analysis of x-ray magnetic circular dichroism spectra performed via the spin moment sum rule. Fully relativistic Korringa-Kohn-Rostoker Green's function calculations for Co monolayers and adatoms on Cu, Pd, Ag, Pt, and Au (111) surfaces were performed to verify whether the sum over magnetic dipole terms Tx+Ty+Tz is zero and whether the angular dependence of the Tα term goes as 3 cos2θ -1 . It follows that there are circumstances when the influence of the SOC on Tα cannot be neglected even for 3 d atoms where the SOC is nominally small. The crucial factor appears to be the dimensionality of the system: For 3 d adatoms, the influence of SOC on Tα can be significant whereas for monolayers it is always practically negligible. Apart from the dimensionality, hybridization between adatom and substrate states is also important: Small hybridization enhances the importance of the SOC and vice versa.

  20. Quench problems of Nb3 Sn cosine theta high field dipole model magnets

    SciTech Connect

    Yamada, Ryuji; Wake, Masayoshi; /KEK, Tsukuba

    2004-12-01

    We have developed and tested several cosine theta high field dipole model magnets for accelerator application, utilizing Nb{sub 3}Sn strands made by MJR method and PIT method. With Rutherford cables made with PIT strand we achieved 10.1 Tesla central field at 2.2 K operation, and 9.5 Tesla at 4.5 K operation. The magnet wound with the MJR cable prematurely quenched at 6.8 Tesla at 4.5 K due to cryo-instability. Typical quench behaviors of these magnets are described for both types of magnets, HFDA-04 of MJR and HFDA-05 of PIT. Their characteristics parameters are compared on d{sub eff}, RRR, thermal conductivity and others, together with other historical Nb{sub 3}Sn magnets. It is suggested a larger RRR value is essential for the stability of the epoxy impregnated high field magnets made with high current density strands. It is shown that a magnet with a larger RRR value has a longer MPZ value and more stable, due to its high thermal conductivity and low resistivity.

  1. 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.

  2. Second order optical nonlinearity of graphene due to electric quadrupole and magnetic dipole effects.

    PubMed

    Cheng, J L; Vermeulen, N; Sipe, J E

    2017-03-06

    We present a practical scheme to separate the contributions of the electric quadrupole-like and the magnetic dipole-like effects to the forbidden second order optical nonlinear response of graphene, and give analytic expressions for the second order optical conductivities, calculated from the independent particle approximation, with relaxation described in a phenomenological way. We predict strong second order nonlinear effects, including second harmonic generation, photon drag, and difference frequency generation. We discuss in detail the controllability of these effects by tuning the chemical potential, taking advantage of the dominant role played by interband optical transitions in the response.

  3. Second order optical nonlinearity of graphene due to electric quadrupole and magnetic dipole effects

    PubMed Central

    Cheng, J. L.; Vermeulen, N.; Sipe, J. E.

    2017-01-01

    We present a practical scheme to separate the contributions of the electric quadrupole-like and the magnetic dipole-like effects to the forbidden second order optical nonlinear response of graphene, and give analytic expressions for the second order optical conductivities, calculated from the independent particle approximation, with relaxation described in a phenomenological way. We predict strong second order nonlinear effects, including second harmonic generation, photon drag, and difference frequency generation. We discuss in detail the controllability of these effects by tuning the chemical potential, taking advantage of the dominant role played by interband optical transitions in the response. PMID:28262762

  4. Direct measurement of excited-state dipole matrix elements using electromagnetically induced transparency in the hyperfine Paschen-Back regime

    NASA Astrophysics Data System (ADS)

    Whiting, Daniel J.; Keaveney, James; Adams, Charles S.; Hughes, Ifan G.

    2016-04-01

    Applying large magnetic fields to gain access to the hyperfine Paschen-Back regime can isolate three-level systems in a hot alkali metal vapors, thereby simplifying usually complex atom-light interactions. We use this method to make the first direct measurement of the |<5 P ||e r ||5 D >| matrix element in 87Rb. An analytic model with only three levels accurately models the experimental electromagnetically induced transparency spectra and extracted Rabi frequencies are used to determine the dipole matrix element. We measure |<5 P3 /2||e r ||5 D5 /2>| =(2.290 ±0 .002stat±0 .04syst) e a0 , which is in excellent agreement with the theoretical calculations of Safronova, Williams, and Clark [Phys. Rev. A 69, 022509 (2004), 10.1103/PhysRevA.69.022509].

  5. Magnetically excited flexural plate wave apparatus

    DOEpatents

    Martin, Stephen J.; Butler, Michael A.; Frye, Gregory C.; Smith, James H.

    1998-01-01

    A non-piezoelectric flexural plate wave apparatus having meander-line transducers mounted on a non-piezoelectric membrane. A static magnetic field is directed perpendicularly to the conductive legs of the transducers in the plane of the membrane. Single-port, two-port, resonant, non-resonant, eigenmode, and delay-line modes may be employed.

  6. Magnetically excited flexural plate wave apparatus

    DOEpatents

    Martin, S.J.; Butler, M.A.; Frye, G.C.; Smith, J.H.

    1998-11-17

    A non-piezoelectric flexural plate wave apparatus having meander-line transducers mounted on a non-piezoelectric membrane is disclosed. A static magnetic field is directed perpendicularly to the conductive legs of the transducers in the plane of the membrane. Single-port, two-port, resonant, non-resonant, eigenmode, and delay-line modes may be employed. 15 figs.

  7. 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.

  8. 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.

  9. Imparting magnetic dipole heterogeneity to internalized iron oxide nanoparticles for microorganism swarm control

    NASA Astrophysics Data System (ADS)

    Kim, Paul Seung Soo; Becker, Aaron; Ou, Yan; Julius, Anak Agung; Kim, Min Jun

    2015-03-01

    Tetrahymena pyriformis is a single cell eukaryote that can be modified to respond to magnetic fields, a response called magnetotaxis. Naturally, this microorganism cannot respond to magnetic fields, but after modification using iron oxide nanoparticles, cells are magnetized and exhibit a constant magnetic dipole strength. In experiments, a rotating field is applied to cells using a two-dimensional approximate Helmholtz coil system. Using rotating magnetic fields, we characterize discrete cells' swarm swimming which is affected by several factors. The behavior of the cells under these fields is explained in detail. After the field is removed, relatively straight swimming is observed. We also generate increased heterogeneity within a population of cells to improve controllability of a swarm, which is explored in a cell model. By exploiting this straight swimming behavior, we propose a method to control discrete cells utilizing a single global magnetic input. Successful implementation of this swarm control method would enable teams of microrobots to perform a variety of in vitro microscale tasks impossible for single microrobots, such as pushing objects or simultaneous micromanipulation of discrete entities.

  10. Long term magnetic performance of the steel concrete dipoles in LEP

    SciTech Connect

    Billan, J.; Gourber, J.P.; Henrichsen, K.N.

    1994-07-01

    The steel-concrete cores of the LEP bending magnets were built of regularly spaced steel laminations, the spaces being filled with cement mortar. The effects of compressive stresses were studied on models and the long term behavior has been monitored during operation of the LEP machine over a period of four years. The requirements for stability and reproducibility of the magnetic field have increased in step with the development of the accelerator and its particle detectors. After the initial aging in the LEP tunnel, the most important parameter was the temperature coefficient. The temperatures of a number of magnet cores are therefore continuously monitored and corrections are applied to the indicated value of particle momentum as measured by NMR and a flip coil in a reference dipole connected in series with the bending magnets. This reference magnet is in turn calibrated periodically by a direct measurement of flux variations in a loop mounted in the lower poles of all bending magnets installed in the tunnel

  11. E -band excitations in the magnetic Keplerate molecule Fe30

    NASA Astrophysics Data System (ADS)

    Waldmann, O.

    2007-01-01

    Low-temperature excitations in the magnetic Keplerate molecule Fe30 as calculated by linear spin-wave theory (SWT), modified linear SWT, and spin-level mean-field theory (SLMFT) are compared to recent inelastic neutron scattering results by Garlea [Phys. Rev. B 73, 024414 (2006)]. SLMFT reproduces a part of the experimental spectrum rather well, but not all of it. SWTs yield a small fraction of the E -band excitations and hence are not capable of a complete description of the excitation spectrum.

  12. 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

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

    SciTech Connect

    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 dipole resonances in the emerging THz all-dielectric metamaterial technology.

  14. Magnetic g_e-FACTORS and Electric Dipole Moments of Lanthanide Monoxides: PrO

    NASA Astrophysics Data System (ADS)

    Wang, Hailing; Steimle, Timothy C.; Linton, Colan

    2009-06-01

    The very complex optical spectra of the lanthanide monoxides are caused by the insensitivity of the electronic energies to the numerous possible arrangements of the Ln^{2+} electrons in the 4f and 6s orbitals. Disentangling the complex optical spectra may be aided by using simple Ligand Field Theory(LFT) to establish the global electronic structure for the low-lying electronic states. A comparison of experimentally determined permanent electric dipole moments, μ_{el}, and magnetic dipole moments, μ_{m}, is an effective means of sorting this myriad of states and assessing the quality of LFT and other electronic structure methodologies. Here we report on the determination of the permanent electric dipole moments, μ_{el}, and magnetic g{_e}-factors for the X_{2}(Ω = 4.5) and [18.1] (Ω = 5.5) states of PrO from the analysis of the optical Stark and Zeeman spectra. The g_{e}-factors are compared with those computed using wavefunctions predicted from ligand field theory. The μ_{el} value for the X_{2}(Ω = 4.5) state is compared to ab initio, and density functional predictions and with the experimental values of other lanthanide monoxides. A phenomenological fit of μ_{el} for the entire series of LnO is used to predict μ_{el} for the isovalent actinide monoxide series. Carette, P.,; Hocquet,A. J. Mol. Spectrosc. 131 301, 1988. Dolg, M.; Stoll, H. Theor. Chim. Acta. 75,369, 1989. Wu, Z.; Guan, W. Meng, J. Su, Z. J. Cluster Science 18 444, 2007.

  15. Observation of the Forbidden Magnetic Dipole Transition 6{sup 2}P{sub ½} --> 7{sup 2}P{sub ½} in Atomic Thallium

    DOE R&D Accomplishments Database

    Chu, S.

    1976-10-01

    A measurement of the 6{sup 2}P{sub ½} --> 7{sup 2}P{sub ½} forbidden magnetic dipole matrix element in atomic thallium is described. A pulsed, linearly polarized dye laser tuned to the transition frequency is used to excite the thallium vapor from the 6{sup 2}P{sub ½} ground state to the 7{sup 2}P{sub ½} excited state. Interference between the magnetic dipole M1 amplitude and a static electric field induced E1 amplitude results in an atomic polarization of the 7{sup 2}P{sub ½} state, and the subsequent circular polarization of 535 nm fluorescence. The circular polarization is seen to be proportional to / as expected, and measured for several transitions between hyperfine levels of the 6{sup 2}P{sub ½} and 7{sup 2}P{sub ½} states. The result is = -(2.11 +- 0.30) x 10{sup -5} parallel bar e parallel bar dirac constant/2mc, in agreement with theory.

  16. The permanent electric dipole moments and magnetic g factors of uranium monoxide

    NASA Astrophysics Data System (ADS)

    Heaven, Michael C.; Goncharov, Vasiliy; Steimle, Timothy C.; Ma, Tongmei; Linton, Colan

    2006-11-01

    Permanent electric dipole moments and magnetic g factors for uranium monoxide (UO) have been determined from analyses of optical Stark and Zeeman spectra recorded at a spectral resolution that approaches the natural linewidth limit. Numerous branch features in the previously characterized [L. A. Kaledin et al., J. Mol. Spectrosc. 164, 27 (1994)] (0,0) [18403]5-X(1)4 and (0,0) [18404]5-X(1)4 electronic transitions were recorded in the presence of tunable static electric (Stark effect) or magnetic (Zeeman effect) fields. The lines exhibited unusually large Zeeman tuning effects. A ligand field model and an ab initio electronic structure calculation [R. Tyagi, Ph.D. thesis, The Ohio State University (2005)] were used to interpret the ground state properties. The results indicate that the low energy electronic states of UO are sufficiently ionic for the meaningful application of ligand field theory models. The dipole moments and g factors were distinctly different for the three electronic states examined, which implies that these properties may be used to deduce the underlying electronic state configurations.

  17. A genetic algorithm based determination of the ground and excited (1Lb) state structure and the orientation of the transition dipole moment of benzimidazole.

    PubMed

    Schmitt, Michael; Krügler, Daniel; Böhm, Marcel; Ratzer, Christian; Bednarska, Violetta; Kalkman, Ivo; Meerts, W Leo

    2006-01-14

    The structure of benzimidazole has been determined in the electronic ground and excited states using rotationally resolved electronic spectroscopy. The rovibronic spectra of four isotopomers and subsequently the structure of benzimidazole have been automatically assigned and fitted using a genetic algorithm based fitting strategy. The lifetimes of the deuterated isotopomers have been shown to depend on the position of deuteration. The angle of the transition dipole moment with the inertial a-axis could be determined to be -30 degrees. Structures and transition dipole moment orientation have been calculated at various levels of theory and were compared to the experimental results.

  18. Estimation of Ground-State and Singlet Excited-State Dipole Moments of Substituted Schiff Bases Containing Oxazolidin-2-one Moiety through Solvatochromic Methods.

    PubMed

    Kumari, Rekha; Varghese, Anitha; George, Louis

    2017-01-01

    Absorption and fluorescence studies on novel Schiff bases (E)-4-(4-(4-nitro benzylideneamino)benzyl)oxazolidin-2-one (NBOA) and (E)-4-(4-(4-chlorobenzylidene amino)benzyl)oxazolidin-2-one (CBOA) were recorded in a series of twelve solvents upon increasing polarity at room temperature. Large Stokes shift indicates bathochromic fluorescence band for both the molecules. The photoluminescence properties of Schiff bases containing electron withdrawing and donating substituents were analyzed. Intramolecular charge transfer behavior can be studied based on the influence of different substituents in Schiff bases. Changes in position and intensity of absorption and fluorescence spectra are responsible for the stabilization of singlet excited-states of Schiff base molecules with different substituents, in polar solvents. This is attributed to the Intramolecular charge transfer (ICT) mechanism. In case of electron donating (-Cl) substituent, ICT contributes largely to positive solvatochromism when compared to electron withdrawing (-NO2) substituent. Ground-state and singlet excited-state dipole moments of NBOA and CBOA were calculated experimentally using solvent polarity function approaches given by Lippert-Mataga, Bakhshiev, Kawskii-Chamma-Viallet and Reichardt. Due to considerable π- electron density redistribution, singlet excited-state dipole moment was found to be greater than ground-state dipole moment. Ground-state dipole moment value which was determined by quantum chemical method was used to estimate excited-state dipole moment using solvatochromic correlations. Kamlet-Abboud-Taft and Catalan multiple linear regression approaches were used to study non-specific solute-solvent interaction and hydrogen bonding interactions in detail. Optimized geometry and HOMO-LUMO energies of NBOA and CBOA have been determined by DFT and TD-DFT/PCM (B3LYP/6-311G (d, p)). Mulliken charges and molecular electrostatic potential have also been evaluated from DFT calculations.

  19. 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.

  20. Spin observables for the isovector spin-dipole giant resonance excited in (p,n) reactions at medium energies.

    NASA Astrophysics Data System (ADS)

    Watson, J. W.

    1996-10-01

    For charge-exchange reactions at medium energies, one of the dominant features of small-angle spectra is the excitation of the ΔT = 1, ΔL = 1, ΔS = 1 isovector "spin-dipole" resonance (SDR). We describe how polarization-transfer measurements can be used to identify the overlapping J^π = 0^-, 1^-, and 2^- components of the SDR. Results for ^16O(p,n) and ^40Ca(p,n) using data (J. W. Watson et al.), Nucl. Phys. A577, 79c (1994). (J. W. Watson et al.), Nucl. Phys. A599, 211c (1996). for the transverse polarization-transfer coefficient D_NN' are presented and compared with distorted-wave impulse approximation (DWIA) calculations with theory of finite Fermi systems (TFFS) wavefunctions. (F. A. Gareev et al.), Sov. J. Part. Nucl. 19, 373 (1988). Future experiments will utilize complete sets of polarization-transfer data to extract the longitudinal and transverse spin responses,(M. Ichimura and K. Kawahigashi, Phys. Rev. C45), 1822 (1992). which will provide a more definitive separation of the different J^πs in the SDR. footnote Supported by NSF PHY 94-09265

  1. On the Estimation of Excited-State Dipole Moments from Solvatochromic Shifts of Absorption and Fluorescence Spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.

    2002-05-01

    The effect of the solvent polarity parameters f (Ɛ, n) and ᵩ(Ɛ, n) appearing in solvatochromic theories, and the effect of the molecular shape of the Onsager cavity (sphere, ellipsoid of revolution) on the determined electric dipole moments μe in the singlet excited state are studied. It is found that the shape of the solute does not exhibit a significant effect on the determined values of μe, but only on the solvent parameters f (Ɛ, n) and ᵩ(Ɛ, n) as well as on the Onsager radius a. Passing from a sphere to an ellipsoid leads to such a change in the scale that induces a proportional change in the slope coefficients m1 and m2. Also the effect of α/a3 (a and a are the mean isotropic polarizability of the solute and the Onsager cavity radius in a homogeneous dielectric, respectively) on the determined values of m e has been studied, and it is found that the assumption α/a3 = 1/2 is valid in many cases.

  2. Measurements of Dipole Excitations in ^48Ca Between Eγ = 9.5 and 15.3 MeV

    NASA Astrophysics Data System (ADS)

    Tompkins, J. R.; Arnold, C. W.; Karwowski, H. J.; Rich, G. C.; Howell, C. R.; Sobotka, L. G.

    2010-02-01

    ^48Ca photodisintegration cross sections were measured using γ-ray beams of 34 different energies between 9.5 and 15.3 MeV generated with the TUNL High-Intensity γ-ray Source (HIγS). The cross sections were measured with a 2.7 g ^48Ca target enriched to 92% using an array of ^3He proportional-counters embedded in thermalizing polyethylene. The absolute cross sections for the ^48Ca(γ,n) reaction were obtained by normalization to the well known ^2H(γ,n) reaction cross sections. Single neutron emission is the dominant channel in this energy range and its detection provides a measurement of dipole excitation strength such as the previously identified M1 strength at Eγ = 10.22 MeV,footnotetextW.Steffen et al. Nucl. Phys. A 404, 413 (1983). for which a new value will be presented. Structures on the low-energy tail of the E1 GDR were also observed and will be presented. )

  3. Quantum magnetic excitations from stripes in copper-oxide superconductors

    NASA Astrophysics Data System (ADS)

    Tranquada, John

    2005-03-01

    Recent inelastic neutron scattering studies show that the magnetic excitation spectra of two well-studied families of cuprate superconductors are much more similar than previously believed. In particular, I will present results we have obtained on La2-xBaxCuO4 (LBCO) with x = 0.125 [1,2]. Using very large single crystals grown at Brookhaven, we were able to measure the magnetic excitations up to 200 meV using the MAPS time-of-flight spectrometer at the ISIS spallation source. While the lowest energy excitations are split incommensurately, these disperse inwards towards the antiferromagnetic wave vector with increasing energy, merging at ˜50 meV. At higher energies the excitations disperse outwards again. There is a significant enhancement of the Q-integrated magnetic scattering near ˜50 meV compared to lower energies, suggestive of quantum correlations and distinct from spin-wave predictions. Many features of the spectrum are quite similar to those found in YBa2Cu3O6.6 [3]. One can qualitatively characterize the results with a universal excitation spectrum, together with a material-dependent spin gap in the superconducting state. It is important to note that the LBCO sample exhibits static stripe order [2], as this has significant implications for the origin of the magnetic excitations in superconducting cuprates. *J. M. Tranquada, H. Woo, T. G. Perring, H. Goka, G. D. Gu, G. Xu, M. Fujita, and K. Yamada, Nature 429, 534 (2004). *M. Fujita, H. Goka, K. Yamada, J. M. Tranquada, and L.-P. Regnault, Phys. Rev. B 70, 104517 (2004). *S. M. Hayden, H. A. Mook, P. C. Dai, T. G. Perring, and F. Dogan, Nature 429, 531 (2004).

  4. Didactic Considerations on Magnetic Circuits Excited by Permanent Magnets

    ERIC Educational Resources Information Center

    Barmada, S.; Rizzo, R.; Sani, L.

    2009-01-01

    In this paper, the authors focus their attention on the way magnetic circuits and permanent magnets are usually treated in most textbooks and electrical engineering courses. This paper demonstrates how this important topic is too often presented simplistically. This simplistic treatment does not allow the students to develop a complete…

  5. A study of beam position diagnostics using beam-excited dipole modes in third harmonic superconducting accelerating cavities at a free-electron laser

    SciTech Connect

    Zhang Pei; Baboi, Nicoleta; Jones, Roger M.; Shinton, Ian R. R.; Flisgen, Thomas; Glock, Hans-Walter

    2012-08-15

    We investigate the feasibility of beam position diagnostics using higher order mode (HOM) signals excited by an electron beam in the third harmonic 3.9 GHz superconducting accelerating cavities at FLASH. After careful theoretical and experimental assessment of the HOM spectrum, three modal choices have been narrowed down to fulfill different diagnostics requirements. These are localized dipole beam-pipe modes, trapped cavity modes from the fifth dipole band, and propagating modes from the first two dipole bands. These modes are treated with various data analysis techniques: modal identification, direct linear regression (DLR), and singular value decomposition (SVD). Promising options for beam diagnostics are found from all three modal choices. This constitutes the first prediction, subsequently confirmed by experiments, of trapped HOMs in third harmonic cavities, and also the first direct comparison of DLR and SVD in the analysis of HOM-based beam diagnostics.

  6. A study of beam position diagnostics using beam-excited dipole modes in third harmonic superconducting accelerating cavities at a free-electron laser.

    PubMed

    Zhang, Pei; Baboi, Nicoleta; Jones, Roger M; Shinton, Ian R R; Flisgen, Thomas; Glock, Hans-Walter

    2012-08-01

    We investigate the feasibility of beam position diagnostics using higher order mode (HOM) signals excited by an electron beam in the third harmonic 3.9 GHz superconducting accelerating cavities at FLASH. After careful theoretical and experimental assessment of the HOM spectrum, three modal choices have been narrowed down to fulfill different diagnostics requirements. These are localized dipole beam-pipe modes, trapped cavity modes from the fifth dipole band, and propagating modes from the first two dipole bands. These modes are treated with various data analysis techniques: modal identification, direct linear regression (DLR), and singular value decomposition (SVD). Promising options for beam diagnostics are found from all three modal choices. This constitutes the first prediction, subsequently confirmed by experiments, of trapped HOMs in third harmonic cavities, and also the first direct comparison of DLR and SVD in the analysis of HOM-based beam diagnostics.

  7. Sequential CD34 cell fractionation by magnetophoresis in a magnetic dipole flow sorter

    PubMed Central

    Schneider, Thomas; Karl, Stephan; Moore, Lee R.; Chalmers, Jeffrey J.; Williams, P. Stephen; Zborowski, Maciej

    2010-01-01

    Cell separation and fractionation based on fluorescent and magnetic labeling procedures are common tools in contemporary research. These techniques rely on binding of fluorophores or magnetic particles conjugated to antibodies to target cells. Cell surface marker expression levels within cell populations vary with progression through the cell cycle. In an earlier work we showed the reproducible magnetic fractionation (single pass) of the Jurkat cell line based on the population distribution of CD45 surface marker expression. Here we present a study on magnetic fractionation of a stem and progenitor cell (SPC) population using the established acute myelogenous leukemia cell line KG-1a as a cell model. The cells express a CD34 cell surface marker associated with the hematopoietic progenitor cell activity and the progenitor cell lineage commitment (related to the CD34 marker expression level). The CD34 expression level is approximately an order of magnitude lower than that of the CD45 marker, which required further improvements of the magnetic fractionation apparatus. The cells were immuno-magnetically labeled using a sandwich of anti CD34 antibody-phycoerythrin (PE) conjugate and anti PE magnetic nanobead and fractionated into eight components using a continuous flow dipole magnetophoresis apparatus. The CD34 marker expression distribution between sorted fractions was measured by quantitative PE flow cytometry (using QuantiBRITE™ PE calibration beads), and it was shown to be correlated with the cell magnetophoretic mobility distribution. A flow outlet addressing scheme based on the concept of the transport lamina thickness was used to control cell distribution between the eight outlet ports. The fractional cell distributions showed good agreement with numerical simulations of the fractionation based on the cell magnetophoretic mobility distribution in the unsorted sample. PMID:20024182

  8. Transient magnetization of core excited organic molecules adsorbed on graphene

    NASA Astrophysics Data System (ADS)

    Ravikumar, Abhilash; Baby, Anu; Lin, He; Brivio, Gian Paolo; Fratesi, Guido

    This work presents a density functional theory based computational investigation of electronic and magnetic properties of physisorbed and chemisorbed organic molecules on graphene in the ground state and core excited one at low molecular coverage. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, it is found that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the contrary, when graphene is covalently functionalized, the system is magnetic in the ground state presenting two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore. This project has received funding from the European Union Seventh Framework Programme under grant agreement n∘ 607232 [THINFACE].

  9. 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

  10. 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.

  11. Implications of stochastic magnetization dynamics on reliability of dipole coupled nanomagnetic logic

    NASA Astrophysics Data System (ADS)

    Salehi Fashami, Mohammad; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2013-03-01

    Straintronic nanomagnetic logic (SML), where Boolean computation is elicited from dipole coupled multiferroic nanomagnets switched with electrically generated strain, has emerged as an extremely energy-efficient computing paradigm. We have studied the reliability of such logic circuits by computing the gate error rates in the presence of thermal noise by simulating switching trajectories with the stochastic Landau-Lifshitz-Gilbert (LLG) equation. In addition, we examine the lower bound of energy dissipation as a function of switching error and explain how the out-of-plane excursion of the magnetization vector leads to excess energy dissipation over this bound for a given switching error. This analysis is performed to understand the connection between reliability and energy dissipation for a single switch and then extended to larger nanomagnetic logic circuits to assess the viability of dipole coupled SML. This work is supported by the US National Science Foundation under the SHF-Small grant CCF-1216614, NEB 2020 grant ECCS-1124714 and by the Semiconductor Research Corporation (SRC) under NRI Task 2203.001.

  12. Solvent effects on the absorption and fluorescence spectra of some laser dyes: estimation of ground and excited-state dipole moments.

    PubMed

    Thipperudrappa, J; Biradar, D S; Manohara, S R; Hanagodimath, S M; Inamadar, S R; Manekutla, R J

    2008-03-01

    The absorption and fluorescence spectra of three extensively used laser dyes namely 1,1,4,4-tetraphenyl-1,3-butadiene (TPB), 2-(4'-t-butylphenyl)-5-(4''-biphenylyl)-1-oxa-3,4-diazole (BPBD), 1,4-bis[2-(2-methylphenyl)ethenyl]-benzene (Bis-MSB) have been recorded at room temperature (300K) in solvents of different polarities. The effects of the solvents upon the spectral properties are discussed. The ground-state dipole moments (mu(g)) were determined experimentally by Guggenheim and Higasi method separately and were compared with theoretical values obtained using quantum chemical method. The ground-state dipole moments obtained by using Guggenheim method were then used in the estimation of excited-state dipole moments (mu(e)) by using Lippert's, Bakhshiev's and Kawski-Chamma-Viallet's equations. In all the above three equations the variation of the Stokes shift with the solvent dielectric constant and refractive index was made use of. It was observed that dipole moments of excited state were higher than those of the ground state for all the dyes.

  13. Effect of solvents on the spectroscopic properties of LD-489 & LD-473: Estimation of ground and excited state dipole moments by solvatochromic shift method

    NASA Astrophysics Data System (ADS)

    Deepa, H. R.; Thipperudrappa, J.; Suresh Kumar, H. M.

    2013-05-01

    The absorption and fluorescence spectra of 6,7,8,9-tetrahydro-6,8,9-trimethyl-4-(trifluoro methyl)-2H-pyrano[2,3-b][1,8]naphthyridin-2-one (LD-489) and 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H-pyrrolo[3,2-g]quinolin-7-one (LD-473) have been recorded at room temperature in different solvents and 1,4-dioxane-acetonitrile solvent mixtures. The UV-Visible absorption spectra are less sensitive to solvent polarity than the corresponding fluorescence spectra in both the dyes which show pronounced solvatochromic effect. The effects of solvents upon the spectral properties are analyzed using Lippert-Mataga polarity function, Richardts microscopic solvent polarity parameter and Catalán's multiple linear regression approach. Both general solute-solvent interactions and specific interactions are operative in these systems. The solvatochromic correlations are used to estimate excited state dipole moments using experimentally determined ground state dipole moments. The excited state dipole moment for both the dyes are found to be larger than their corresponding ground state dipole moment and is interpreted based on their resonance structures.

  14. Solvent effects on the absorption and fluorescence spectra of some laser dyes: Estimation of ground and excited-state dipole moments

    NASA Astrophysics Data System (ADS)

    Thipperudrappa, J.; Biradar, D. S.; Manohara, S. R.; Hanagodimath, S. M.; Inamadar, S. R.; Manekutla, R. J.

    2008-03-01

    The absorption and fluorescence spectra of three extensively used laser dyes namely 1,1,4,4-tetraphenyl-1,3-butadiene (TPB), 2-(4'- t-butylphenyl)-5-(4″-biphenylyl)-1-oxa-3,4-diazole (BPBD), 1,4-bis[2-(2-methylphenyl)ethenyl]-benzene (Bis-MSB) have been recorded at room temperature (300 K) in solvents of different polarities. The effects of the solvents upon the spectral properties are discussed. The ground-state dipole moments ( μg) were determined experimentally by Guggenheim and Higasi method separately and were compared with theoretical values obtained using quantum chemical method. The ground-state dipole moments obtained by using Guggenheim method were then used in the estimation of excited-state dipole moments ( μe) by using Lippert's, Bakhshiev's and Kawski-Chamma-Viallet's equations. In all the above three equations the variation of the Stokes shift with the solvent dielectric constant and refractive index was made use of. It was observed that dipole moments of excited state were higher than those of the ground state for all the dyes.

  15. Interior Permanent Magnet Reluctance Machine with Brushless Field Excitation

    SciTech Connect

    Wiles, R.H.

    2005-10-07

    In a conventional permanent magnet (PM) machine, the air-gap flux produced by the PM is fixed. It is difficult to enhance the air-gap flux density due to limitations of the PM in a series-magnetic circuit. However, the air-gap flux density can be weakened by using power electronic field weakening to the limit of demagnetization of the PMs. This paper presents the test results of controlling the PM air-gap flux density through the use of a stationary brushless excitation coil in a reluctance interior permanent magnet with brushless field excitation (RIPM-BFE) motor. Through the use of this technology the air-gap flux density can be either enhanced or weakened. There is no concern with demagnetizing the PMs during field weakening. The leakage flux of the excitation coil through the PMs is blocked. The prototype motor built on this principle confirms the concept of flux enhancement and weakening through the use of excitation coils.

  16. Sequential CD34 cell fractionation by magnetophoresis in a magnetic dipole flow sorter.

    PubMed

    Schneider, Thomas; Karl, Stephan; Moore, Lee R; Chalmers, Jeffrey J; Williams, P Stephen; Zborowski, Maciej

    2010-01-01

    Cell separation and fractionation based on fluorescent and magnetic labeling procedures are common tools in contemporary research. These techniques rely on binding of fluorophores or magnetic particles conjugated to antibodies to target cells. Cell surface marker expression levels within cell populations vary with progression through the cell cycle. In an earlier work we showed the reproducible magnetic fractionation (single pass) of the Jurkat cell line based on the population distribution of CD45 surface marker expression. Here we present a study on magnetic fractionation of a stem and progenitor cell (SPC) population using the established acute myelogenous leukemia cell line KG-1a as a cell model. The cells express a CD34 cell surface marker associated with the hematopoietic progenitor cell activity and the progenitor cell lineage commitment. The CD34 expression level is approximately an order of magnitude lower than that of the CD45 marker, which required further improvements of the magnetic fractionation apparatus. The cells were immunomagnetically labeled using a sandwich of anti-CD34 antibody-phycoerythrin (PE) conjugate and anti-PE magnetic nanobead and fractionated into eight components using a continuous flow dipole magnetophoresis apparatus. The CD34 marker expression distribution between sorted fractions was measured by quantitative PE flow cytometry (using QuantiBRITE PE calibration beads), and it was shown to be correlated with the cell magnetophoretic mobility distribution. A flow outlet addressing scheme based on the concept of the transport lamina thickness was used to control cell distribution between the eight outlet ports. The fractional cell distributions showed good agreement with numerical simulations of the fractionation based on the cell magnetophoretic mobility distribution in the unsorted sample.

  17. Interfacial Phenomena of Magnetic Fluid with Permanent Magnet in a Longitudinally Excited Container

    SciTech Connect

    Sudo, Seiichi; Wakuda, Hirofumi; Yano, Tetsuya

    2008-02-21

    This paper describes the magnetic fluid sloshing in a longitudinally excited container. Liquid responses of magnetic fluid with a permanent magnet in a circular cylindrical container subject to vertical vibration are investigated. Experiments are performed on a vibration- testing system which provided longitudinal excitation. A cylindrical container made with the acrylic plastic is used in the experiment. A permanent magnet is in the state of floating in a magnetic fluid. The disk-shaped and ring-shaped magnets are examined. The different interfacial phenomena from the usual longitudinal liquid sloshing are observed. It is found that the wave motion frequency of magnetic fluid with a disk-shaped magnet in the container subject to vertical vibration is exactly same that of the excitation. In the case of ring-shaped magnet, the first symmetrical mode of one-half subharmonic response is dominant at lower excitation frequencies. The magnetic fluid disintegration of the free surface was also observed by a high-speed video camera system.

  18. Similarity transformation approach for ferromagnetic mixed convection flow in the presence of chemically reactive magnetic dipole

    NASA Astrophysics Data System (ADS)

    Hayat, Tasawar; Ijaz Khan, Muhammad; Imtiaz, Maria; Alsaedi, Ahmed; Waqas, Muhammad

    2016-10-01

    A simple model of chemical reactions for two dimensional ferrofluid flows is constructed. The impact of magnetic dipole and mixed convection is further analyzed. Flow is caused by linear stretching of the sheet. Similarity transformation is adopted to convert the partial differential equations into ordinary differential equations and then solved by Euler's explicit method. The characteristics of sundry parameters on the velocity, temperature, and concentration fields are graphically elaborated. It is noted that the impact of magneto-thermomechanical interaction is to slow down the fluid motion. The skin friction coefficient enhances and affects the rate of heat transfer. For higher values of ferrohydrodynamics, the interaction velocity shows decreasing behavior. Further the Prandtl number on temperature has opposite behavior when compared with thermal radiation and ferrohydrodynamics interaction.

  19. 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.

  20. New measurements of sextupole field decay and snapback effect on Tevatron dipole magnets

    SciTech Connect

    Velev, G.V.; Bauer, P.; Carcagno, R.; DiMarco, J.; Lamm, M.; Orris, D.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Tompkins, J.; /Fermilab

    2006-07-01

    To perform detailed studies of the dynamic effects in superconducting accelerator magnets, a fast continuous harmonics measurement system based on the application of a digital signal processor (DSP) has been built at Fermilab. Using this new system, the dynamic effects in the sextupole field, such as the field decay during the dwell at injection and the rapid subsequent ''snapback'' during the first few seconds of the energy ramp, are evaluated for more than ten Tevatron dipoles from the spare pool. The results confirm the previously observed fast drift in the first several seconds of the sextupole decay and provide additional information on a scaling law for predicting snapback duration. The information presented here can be used for an optimization of the Tevatron and for future LHC operations.

  1. Mass and magnetic dipole moment of negative-parity heavy baryons with spin-3/2

    NASA Astrophysics Data System (ADS)

    Azizi, K.; Sundu, H.

    2017-01-01

    We calculate the mass and residue of the heavy spin-3/2 negative-parity baryons with single heavy bottom or charm quark by use of a two-point correlation function. We use the obtained results to investigate the diagonal radiative transitions among the baryons under consideration. In particular, we compute corresponding transition form factors via light cone QCD sum rules, which are then used to obtain the magnetic dipole moments of the heavy spin-3/2 negative-parity baryons. We remove the pollutions coming from the positive-parity spin-3/2 and positive/negative-parity spin-1/2 baryons by constructing sum rules for different Lorentz structures. We compare the results obtained with the existing theoretical predictions.

  2. Absolute measurement of the relativistic magnetic dipole transition energy in heliumlike argon.

    PubMed

    Amaro, Pedro; Schlesser, Sophie; Guerra, Mauro; Le Bigot, Eric-Olivier; Isac, Jean-Michel; Travers, Pascal; Santos, José Paulo; Szabo, Csilla I; Gumberidze, Alexandre; Indelicato, Paul

    2012-07-27

    The 1s2s (3)S(1)→1s(2) (1)S(0) relativistic magnetic dipole transition in heliumlike argon, emitted by the plasma of an electron-cyclotron resonance ion source, has been measured using a double-flat crystal x-ray spectrometer. Such a spectrometer, used for the first time on a highly charged ion transition, provides absolute (reference-free) measurements in the x-ray domain. We find a transition energy of 3104.1605(77) eV (2.5 ppm accuracy). This value is the most accurate, reference-free measurement done for such a transition and is in good agreement with recent QED predictions.

  3. Magnetic-dipole transitions in highly charged ions as a basis of ultraprecise optical clocks.

    PubMed

    Yudin, V I; Taichenachev, A V; Derevianko, A

    2014-12-05

    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.

  4. 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.

  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. 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.

  7. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Basavaraja, Jana; Suresh Kumar, H. M.; Inamdar, S. R.; Wari, M. N.

    2016-02-01

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π → π* transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μe). It is observed that dipole moment value of excited state (μe) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.

  8. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra.

    PubMed

    Basavaraja, Jana; Kumar, H M Suresh; Inamdar, S R; Wari, M N

    2016-02-05

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π→π⁎ transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μ(e)). It is observed that dipole moment value of excited state (μ(e)) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.

  9. Lymphocyte fractionation using immunomagnetic colloid and a dipole magnet flow cell sorter.

    PubMed

    Moore, L R; Zborowski, M; Sun, L; Chalmers, J J

    1998-09-24

    The relationship between cell function and surface marker expression is a subject of active investigation in biology and medicine. These investigations require separating cells of a homogeneous subset into multiple fractions of varying marker expression. We have developed a novel cell sorter, the dipole magnet flow sorter (DMFS), which separates selected T lymphocyte subpopulations, targeted by immunomagnetic colloid, into multiple fractions according to cell surface marker expression, as determined by flow cytometry. A narrow stream of cells is introduced into a sheath of carrier fluid in a rectangular channel while subjected to a perpendicular magnetic force. The special design of the pole pieces ensures a constant magnetic force acting on the magnetically labeled cells in the separation area. Cells are spread across the flow in relation to their magnetophoretic mobility. Separation is achieved by control of the positions of the effluent stream boundaries, which separate fluid volumes with cells of different magnetophoretic mobility. CD4 and CD8 T lymphocytes labeled with primary antibody-fluorescein isothiocyanate (FITC) conjugate and anti-FITC-magnetic colloid are the chosen cell systems. Flow cytometry analysis shows that, for CD4 cells, a three-fold increase in total marker number per cell is observed when comparing the highest to the lowest fluorescence fractions. Similarly, a four-fold increase in total marker number is observed for CD8 cells. We also observed the separation of two dissimilar cell types that differed in expression of the CD4 marker, monocytes and T helper lymphocytes. We believe that this type of separation is applicable to any cells in suspension for which a suitable antibody exists and, due to the comparatively gentle nature of the process, is particularly suitable for the sorting of fragile cells.

  10. Thermal Hall Effect of Spin Excitations in a Kagome Magnet.

    PubMed

    Hirschberger, Max; Chisnell, Robin; Lee, Young S; Ong, N P

    2015-09-04

    At low temperatures, the thermal conductivity of spin excitations in a magnetic insulator can exceed that of phonons. However, because they are charge neutral, the spin waves are not expected to display a thermal Hall effect. However, in the kagome lattice, theory predicts that the Berry curvature leads to a thermal Hall conductivity κ(xy). Here we report observation of a large κ(xy) in the kagome magnet Cu(1-3, bdc) which orders magnetically at 1.8 K. The observed κ(xy) undergoes a remarkable sign reversal with changes in temperature or magnetic field, associated with sign alternation of the Chern flux between magnon bands. The close correlation between κ(xy) and κ(xx) firmly precludes a phonon origin for the thermal Hall effect.

  11. Collisional excitation of electron Landau levels in strong magnetic fields

    NASA Technical Reports Server (NTRS)

    Langer, S. H.

    1981-01-01

    The cross sections for the excitation and deexcitation of the quantized transverse energy levels of an electron in a magnetic field are calculated for electron-proton and electron-electron collisions in light of the importance of the cross sections for studies of X-ray pulsar emission. First-order matrix elements are calculated using the Dirac theory of the electron, thus taking into account relativistic effects, which are believed to be important in accreting neutron stars. Results for the collisional excitation of ground state electrons by protons are presented which demonstrate the importance of proton recoil and relativistic effects, and it is shown that electron-electron excitations may contribute 10 to 20% of the excitation rate from electron-proton scattering in a Maxwellian plasma. Finally, calculations of the cross section for electron-proton small-angle scattering are presented which lead to relaxation rates for the electron velocity distribution which are modified by the magnetic field, and to a possible increase in the value of the Coulomb logarithm.

  12. Quantum magnetic excitations from stripes in copper oxide superconductors.

    PubMed

    Tranquada, J M; Woo, H; Perring, T G; Goka, H; Gu, G D; Xu, G; Fujita, M; Yamada, K

    2004-06-03

    In the copper oxide parent compounds of the high-transition-temperature superconductors the valence electrons are localized--one per copper site--by strong intra-atomic Coulomb repulsion. A symptom of this localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. Superconductivity appears when mobile 'holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to describing the coexistence, the holes are believed to self-organize into 'stripes' that alternate with antiferromagnetic (insulating) regions within copper oxide planes, which would necessitate an unconventional mechanism of superconductivity. There is an apparent problem with this picture, however: measurements of magnetic excitations in superconducting YBa2Cu3O6+x near optimum doping are incompatible with the naive expectations for a material with stripes. Here we report neutron scattering measurements on stripe-ordered La1.875Ba0.125CuO4. We show that the measured excitations are, surprisingly, quite similar to those in YBa2Cu3O6+x (refs 9, 10) (that is, the predicted spectrum of magnetic excitations is wrong). We find instead that the observed spectrum can be understood within a stripe model by taking account of quantum excitations. Our results support the concept that stripe correlations are essential to high-transition-temperature superconductivity.

  13. Quantum magnetic excitations from stripes in copper oxide superconductors

    NASA Astrophysics Data System (ADS)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-06-01

    In the copper oxide parent compounds of the high-transition-temperature superconductors the valence electrons are localized-one per copper site-by strong intra-atomic Coulomb repulsion. A symptom of this localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. Superconductivity appears when mobile `holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to describing the coexistence, the holes are believed to self-organize into `stripes' that alternate with antiferromagnetic (insulating) regions within copper oxide planes, which would necessitate an unconventional mechanism of superconductivity. There is an apparent problem with this picture, however: measurements of magnetic excitations in superconducting YBa2Cu3O6+x near optimum doping are incompatible with the naive expectations for a material with stripes. Here we report neutron scattering measurements on stripe-ordered La1.875Ba0.125CuO4. We show that the measured excitations are, surprisingly, quite similar to those in YBa2Cu3O6+x (refs 9, 10) (that is, the predicted spectrum of magnetic excitations is wrong). We find instead that the observed spectrum can be understood within a stripe model by taking account of quantum excitations. Our results support the concept that stripe correlations are essential to high-transition-temperature superconductivity.

  14. Collective magnetic excitations of C4-symmetric magnetic states in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Scherer, Daniel D.; Eremin, Ilya; Andersen, Brian M.

    2016-11-01

    We study the collective magnetic excitations of the recently discovered C4-symmetric spin-density-wave states of iron-based superconductors with particular emphasis on their orbital character based on an itinerant multiorbital approach. This is important since the C4-symmetric spin-density-wave states exist only at moderate interaction strengths where damping effects from a coupling to the continuum of particle-hole excitations strongly modify the shape of the excitation spectra compared to predictions based on a local moment picture. We uncover a distinct orbital polarization inherent to magnetic excitations in C4-symmetric states, which provide a route to identify the different commensurate magnetic states appearing in the continuously updated phase diagram of the iron-pnictide family.

  15. 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.

  16. 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.

  17. Terahertz radiation from magnetic excitations in diluted magnetic semiconductors.

    PubMed

    Rungsawang, R; Perez, F; Oustinov, D; Gómez, J; Kolkovsky, V; Karczewski, G; Wojtowicz, T; Madéo, J; Jukam, N; Dhillon, S; Tignon, J

    2013-04-26

    We probed, in the time domain, the THz electromagnetic radiation originating from spins in CdMnTe diluted magnetic semiconductor quantum wells containing high-mobility electron gas. Taking advantage of the efficient Raman generation process, the spin precession was induced by low power near-infrared pulses. We provide a full theoretical first-principles description of spin-wave generation, spin precession, and of emission of THz radiation. Our results open new perspectives for improved control of the direct coupling between spin and an electromagnetic field, e.g., by using semiconductor technology to insert the THz sources in cavities or pillars.

  18. Nonlocal and local magnetization dynamics excited by an RF magnetic field in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Moriyama, Takahiro

    A microwave study in spintronic devices has been actively pursued in the past several years due to the fertile physics and potential applications. On one hand, a passive use of microwave can be very helpful to analyze and understand the magnetization dynamics in spintronic devices. Examples include ferromagnetic resonance (FMR) measurements, and various microwave spectrum analyses in ferromagnetic materials. The most important chrematistic parameter for the phenomenological analysis on the magnetization dynamics is, so called, the Gilbert damping constant. In this work, a relatively new measurement technique, a flip-chip FMR measurement, to conduct the ferromagnetic resonance measurements has been developed. The measurement technique is equally comparable to a conventional FMR measurement. The Gilbert damping constants were extracted for single ferromagnetic layer, spin vale structures, and magnetic tunnel junctions (MTJs). On the other hand, an active use of microwave yields a great potential for interesting phenomena which give new functionalities into spintronic devices. For instance, a spin wave excitation by an rf field can be used to reduce the switching field of a ferromagnet, i.e. microwave assisted magnetization reversal, which could be a potential application in advanced recording media. More interestingly, a precessing magnetization driven by an rf field can generate a pure spin current into a neighboring layer, i.e. spin pumping effect, which is one of the candidates for generating a pure spin current. A ferromagnetic tunnel junction (MTJ) is one of the important devices in spintronics, which is also the key device to investigate the local and nonlocal magnetization dynamics in this work. Therefore, it is also important to develop high quality MTJs. My work starts from the development of MTJ with AlOx and MgO tunnel barriers where it was found it is crucial to find the proper condition for forming a few nanometers thick tunnel barrier. After obtaining

  19. Low-energy dipole excitations in neon isotopes and N=16 isotones within the quasiparticle random-phase approximation and the Gogny force

    SciTech Connect

    Martini, M.; Peru, S.; Dupuis, M.

    2011-03-15

    Low-energy dipole excitations in neon isotopes and N=16 isotones are calculated with a fully consistent axially-symmetric-deformed quasiparticle random phase approximation (QRPA) approach based on Hartree-Fock-Bogolyubov (HFB) states. The same Gogny D1S effective force has been used both in HFB and QRPA calculations. The microscopical structure of these low-lying resonances, as well as the behavior of proton and neutron transition densities, are investigated in order to determine the isoscalar or isovector nature of the excitations. It is found that the N=16 isotones {sup 24}O, {sup 26}Ne, {sup 28}Mg, and {sup 30}Si are characterized by a similar behavior. The occupation of the 2s{sub 1/2} neutron orbit turns out to be crucial, leading to nontrivial transition densities and to small but finite collectivity. Some low-lying dipole excitations of {sup 28}Ne and {sup 30}Ne, characterized by transitions involving the {nu}1d{sub 3/2} state, present a more collective behavior and isoscalar transition densities. A collective proton low-lying excitation is identified in the {sup 18}Ne nucleus.

  20. Spin-torque-driven excitations in magnetic thin films

    NASA Astrophysics Data System (ADS)

    Wang, C.; Seinige, H.; Staudacher, T.; Tsoi, M.

    2011-03-01

    Spin transfer torque (STT) refers to a novel method to control and manipulate magnetic moments using an electrical current. For the past decade it has proven to be a fascinating domain of research with a number of manifestations in various systems interesting both from fundamental science's point of view as well as for technological applications. In ferromagnetic/nonmagnetic (F/N) multilayers a dc electrical current can switch and/or drive its constituent F parts into high-frequency precession which is of interest for microwave and magnetic recording technologies. Interestingly, application of high-frequency currents can also drive the multilayer, e.g., into ferromagnetic resonance (STT-FMR) precession. In our experiments we use point contacts to inject high microwave currents into a variety of magnetic thin films including NiFe/Cu/NiFe/IrMn and NiFe/Cu/Co spin valves, and single ferromagnetic (NiFe or Co) films. The resulting magnetodynamics are detected electrically when a small rectified dc voltage appears across the contact at resonance. We find that in addition to a standard FMR, the microwave currents can excite other resonance modes in our point contacts. We study the behavior of the excitations as a function of applied magnetic field, dc bias current, and microwave frequency. Supported in part by NSF grants DMR-06-45377.

  1. Of dipole antennas in a magnetized plasma in the resonance frequency band

    NASA Astrophysics Data System (ADS)

    Shirokov, E. A.; Chugunov, Yu. V.

    2011-12-01

    We consider characteristics of slow quasielectrostatic waves excited in the resonance frequency band by a source whose dimensions are much less than the wavelength of the electromagnetic wave. We primarily focus on the analysis of the radiation of a harmonic wave in pulsed mode by a dipole source. Firstly, we study the influence of electromagnetic, dispersive, and collisional corrections in the dispersion relation on the field shape. Secondly, we analyze the field structure near the resonance cone. In particular, the effects of the group delay and anomalous spreading of the wave are considered. The developed theory is used to interpret the "OEDIPUS-C" experiment. For example, a delay of 10-4 s and a significant (severalfold) spreading of the pulse were observed at a distance of about ten wavelengths. Finally, some aspects of the inverse problem of electrodynamics are examined. Namely, the role of the smoothness of the antenna charge distribution in the field structure formation is shown and a class of smooth charge distributions creating a given field structure is found.

  2. Decoupling of excitation and receive coils in pulsed magnetic resonance using sinusoidal magnetic field modulation

    NASA Astrophysics Data System (ADS)

    Tseytlin, Mark; Epel, Boris; Sundramoorthy, Subramanian; Tipikin, Dmitriy; Halpern, Howard J.

    2016-11-01

    In pulsed magnetic resonance, the excitation power is many orders of magnitude larger than that induced by the spin system in the receiving coil or resonator. The receiver must be protected during and immediately after the excitation pulse to allow for the energy stored in the resonator to dissipate to a safe level. The time during which the signal is not detected, the instrumental dead-time, can be shortened by using magnetically decoupled excitation and receive coils. Such coils are oriented, with respect to each other, in a way that minimizes the total magnetic flux produced by one coil in the other. We suggest that magnetically decoupled coils can be isolated to a larger degree by tuning them to separate frequencies. Spins are excited at one frequency, and the echo signal is detected at another. Sinusoidal magnetic field modulation that rapidly changes the Larmor frequency of the spins between the excitation and detection events is used to ensure the resonance conditions for both coils. In this study, the relaxation times of trityl-CD3 were measured in a field-modulated pulsed EPR experiment and compared to results obtained using a standard spin echo method. The excitation and receive coils were tuned to 245 and 256.7 MHz, respectively. Using an available rapid-scan, cross-loop EPR resonator, we demonstrated an isolation improvement of approximately 20-30 dB due to frequency decoupling. Theoretical analysis, numerical simulations, and proof-of-concept experiments demonstrated that substantial excitation-detection decoupling can be achieved. A pulsed L-band system, including a small volume bi-modal resonator equipped with modulation coils, was constructed to demonstrate fivefold dead-time reduction in comparison with the standard EPR experiment. This was achieved by detuning of the excitation and receive coils by 26 MHz and using sinusoidal modulation at 480 kHz.

  3. Design, fabrication, and calibration of curved integral coils for measuring transfer function, uniformity, and effective length of LBL ALS (Lawrence Berkeley Laboratory Advanced Light Source) Booster Dipole Magnets

    SciTech Connect

    Green, M.I.; Nelson, D.; Marks, S.; Gee, B.; Wong, W.; Meneghetti, J.

    1989-03-01

    A matched pair of curved integral coils has been designed, fabricated and calibrated at Lawrence Berkeley Laboratory for measuring Advanced Light Source (ALS) Booster Dipole Magnets. Distinctive fabrication and calibration techniques are described. The use of multifilar magnet wire in fabrication integral search coils is described. Procedures used and results of AC and DC measurements of transfer function, effective length and uniformity of the prototype booster dipole magnet are presented in companion papers. 8 refs.

  4. Magnetic antenna excitation of whistler modes. II. Antenna arrays

    SciTech Connect

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

    2014-12-15

    The excitation of whistler modes from magnetic loop antennas has been investigated experimentally. The field topology of the excited wave driven by a single loop antenna has been measured for different loop orientations with respect to the uniform background field. The fields from two or more antennas at different locations are then created by superposition of the single-loop data. It is shown that an antenna array can produce nearly plane waves which cannot be achieved with single antennas. By applying a phase shift along the array, oblique wave propagation is obtained. This allows a meaningful comparison with plane wave theory. The Gendrin mode and oblique cyclotron resonance are demonstrated. Wave helicity and polarization in space and time are demonstrated and distinguished from the magnetic helicity of the wave field. The superposition of two oblique plane whistler modes produces in a “whistler waveguide” mode whose polarization and helicity properties are explained. The results show that single point measurements cannot properly establish the wave character of wave packets. The laboratory observations are relevant for excitation and detection of whistler modes in space plasmas.

  5. Magnetic antenna excitation of whistler modes. II. Antenna arrays

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The excitation of whistler modes from magnetic loop antennas has been investigated experimentally. The field topology of the excited wave driven by a single loop antenna has been measured for different loop orientations with respect to the uniform background field. The fields from two or more antennas at different locations are then created by superposition of the single-loop data. It is shown that an antenna array can produce nearly plane waves which cannot be achieved with single antennas. By applying a phase shift along the array, oblique wave propagation is obtained. This allows a meaningful comparison with plane wave theory. The Gendrin mode and oblique cyclotron resonance are demonstrated. Wave helicity and polarization in space and time are demonstrated and distinguished from the magnetic helicity of the wave field. The superposition of two oblique plane whistler modes produces in a "whistler waveguide" mode whose polarization and helicity properties are explained. The results show that single point measurements cannot properly establish the wave character of wave packets. The laboratory observations are relevant for excitation and detection of whistler modes in space plasmas.

  6. An experimental and theoretical study of excited-state dipole moments of some flavones using an efficient solvatochromic method based on the solvent polarity parameter, ETN

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Jain, Sapan K.; Rastogi, Ramesh C.

    2001-02-01

    The electronic absorption and fluorescence spectra of some biologically active natural flavones have been recorded at room temperature (298 K) in solvents of different polarities. The effects of the solvents upon the spectral properties are discussed. Difference in fluorescence intensity of flavones has been explained on the basis of intersystem crossing and degree of non-planarity calculated theoretically using Austin Model 1 (AM1) method. Excited-state dipole moments have been determined using the solvatochromic method based on the microscopic solvent polarity parameter, ETN. A reasonable agreement has been observed between experimental and AM1 calculated dipole moment changes. Our results are found to be quite reliable in view of the fact that the correlation of the solvatochromic Stokes shifts with microscopic solvent polarity parameter, ETN is superior to that obtained using bulk solvent polarity functions for all the systems studied here.

  7. EXCITATION OF SLOW MODES IN NETWORK MAGNETIC ELEMENTS THROUGH MAGNETIC PUMPING

    SciTech Connect

    Kato, Yoshiaki; Steiner, Oskar; Steffen, Matthias; Suematsu, Yoshinori

    2011-04-01

    From radiation magnetohydrodynamic simulations of the solar atmosphere, we find a new mechanism for the excitation of longitudinal slow modes within magnetic flux concentrations. We find that the convective downdrafts in the immediate surroundings of magnetic elements are responsible for the excitation of slow modes. The coupling between the external downdraft and the plasma motion internal to the flux concentration is mediated by the inertial forces of the downdraft that act on the magnetic flux concentration. These forces, in conjunction with the downward movement, pump the internal atmosphere in the downward direction, which entails a fast downdraft in the photospheric and chromospheric layers of the magnetic element. Subsequent to the transient pumping phase, the atmosphere rebounds, causing a slow mode traveling along the magnetic flux concentration in the upward direction. It develops into a shock wave in chromospheric heights, possibly capable of producing some kind of dynamic fibril. We propose an observational detection of this process.

  8. Excitations in a perfect magnetized quantum spin ladder

    NASA Astrophysics Data System (ADS)

    Zheludev, Andrey; Schmidiger, David; Muehlbauer, Sebastian; Severian, Gvasaliya; Bouillot, Pierre; Kollath, Corinna; Giamarchi, Thierry; Guidi, Tatiana; Bewley, Robert; Ehlers, Georg

    2013-03-01

    The strong-leg S = 1 / 2 Heisenberg spin ladder system C7(D10N)2CuBr4 is investigated in applied magnetic fields using inelastic neutron scattering anf DMRG calculations. The spectrum in the high-field Tomonaga-Luttinger spin liquid phase is found to be qualitatively different from that in the low-field spin gap phase. In the former, numerous spectral featrures, including incommensurate excitations and multi-spinon continua are identified. In contrast, the latter is dominated by long-lived magnon excitations and two-magnon bound states. An unprecedented quantitive agreement between experiment and numerical claculations is achieved. Supported by the Swiss National Fund through MANEP.

  9. Magnetic antenna excitation of whistler modes. I. Basic properties

    SciTech Connect

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

    2014-12-15

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  10. Magnetic antenna excitation of whistler modes. I. Basic properties

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  11. Rotating permanent magnet excitation for blood flow measurement.

    PubMed

    Nair, Sarath S; Vinodkumar, V; Sreedevi, V; Nagesh, D S

    2015-11-01

    A compact, portable and improved blood flow measurement system for an extracorporeal circuit having a rotating permanent magnetic excitation scheme is described in this paper. The system consists of a set of permanent magnets rotating near blood or any conductive fluid to create high-intensity alternating magnetic field in it and inducing a sinusoidal varying voltage across the column of fluid. The induced voltage signal is acquired, conditioned and processed to determine its flow rate. Performance analysis shows that a sensitivity of more than 250 mV/lpm can be obtained, which is more than five times higher than conventional flow measurement systems. Choice of rotating permanent magnet instead of an electromagnetic core generates alternate magnetic field of smooth sinusoidal nature which in turn reduces switching and interference noises. These results in reduction in complex electronic circuitry required for processing the signal to a great extent and enable the flow measuring device to be much less costlier, portable and light weight. The signal remains steady even with changes in environmental conditions and has an accuracy of greater than 95%. This paper also describes the construction details of the prototype, the factors affecting sensitivity and detailed performance analysis at various operating conditions.

  12. R&D steps of a 12-T common coil dipole magnet for SPPC pre-study

    NASA Astrophysics Data System (ADS)

    Wang, Chengtao; Zhang, Kai; Xu, Qingjin

    2016-11-01

    IHEP (the Institute of High Energy Physics, Beijing, China) has started the R&D of high field accelerator magnet technology from 2014 for recently proposed CEPC-SppC (Circular Electron Positron Collider, Super proton-proton Collider) project. The conceptual design study of a 20-T dipole magnet is ongoing with the common coil configuration, and a 12-T model magnet will be fabricated in the next two years. A 3-step R&D process has been proposed to realize this 12-T common-coil model magnet: first, a 12-T subscale magnet will be fabricated with Nb3Sn and NbTi superconductors to investigate the fabrication process and characteristics of Nb3Sn coils, then a 12-T subscale magnet will be fabricated with only Nb3Sn superconductors to test the stress management method and quench protection method of Nb3Sn coils; the final step is fabricating the 12-T common-coil dipole magnet with HTS (YBCO) and Nb3Sn superconductors to test the field optimization method of the HTS and Nb3Sn coils. The characteristics of these R&D steps will be introduced in the paper.

  13. Experimental determination of ground and excited state dipole moments of N, N-bis (2, 5-di-tert-butylphenyl)-3, 4:9, 10-perylenebis (dicarboximide) (DBPI) a photostable laser dye.

    PubMed

    El-Daly, S A; Asiri, A M; Alamry, K A

    2014-07-01

    In the present work, the absorption, emission spectra and dipole moments(μ(g), μ(e)) of N, N-bis (2, 5-di-tert-butylphenyl)-3, 4:9, 10- perylenebis (dicarboximide) (DBPI) have been studied in solvents of various polarities at room temperature. Using the methods of solvatochromism, the difference between the first excited singlet state (μ(e)) and ground state (μ(g)) dipole moments was estimated from Lippert - Mataga,, Bakhshiev, Kawski - Chamma - Viallet equations. The change in dipole moment (Δμ) was also calculated using the variation of the Stokes shift with microscopic solvent polarity parameter (E(T)(N)). It was observed that the value of excited singlet state dipole moment is higher (3.53 Debye) than the ground state one (1.92Debye), showing that the excited state of DBPI is more polar than the ground state.

  14. Magnetic Excitations and the Exchange Energy Available for Superconductivity

    NASA Astrophysics Data System (ADS)

    Dahm, Thomas

    2007-03-01

    We have made detailed comparisons of theoretical calculations and experimental neutron scattering results in absolute units in order to determine the temperature change of the nearest neighbor spin correlations in optimally doped YBCO as one goes from the normal to the superconducting state [1]. This allows us to estimate the magnetic exchange energy change that becomes available for superconducting condensation. Our results show that the available magnetic energy change is about 10-15 times larger than the energy necessary for superconducting condensation [1]. We discuss the issue of the spin sum rule and implications for a spin fluctuation driven pairing interaction as well as implications for low energy excitations in angular photoemission spectroscopy [2]. [1] H. Woo et al, Nature Physics 2, 600 (2006). [2] T. Dahm et al, Phys. Rev. B 72, 214512 (2005).

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

    PubMed

    Bahiraei, Mehdi; Hangi, Morteza

    2016-12-01

    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.

  16. Estimation of ground- and excited-state dipole moments of Nile Red dye from solvatochromic effect on absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Bojarski, P.; Kukliński, B.

    2008-10-01

    The effect of various nonpolar and polar solvents on the location of absorption and fluorescence of Nile Red at room temperature was investigated. Based on the batochromic shift of electronic spectra of Nile Red and Bilot-Kawski theory the following values of ground- and excited-state dipole moments μg = 8.2 ± 1.0 D and μe = 10.0 ± 1.0 D were found. The reasons of high discrepancy between the literature results were discussed.

  17. Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair

    NASA Astrophysics Data System (ADS)

    Chang, Zhiwei; Halle, Bertil

    2013-10-01

    In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water 1H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft

  18. Magnetic sponge phenomena associated with interchain dipole-dipole interactions in a series of ferrimagnetic chain compounds doped with minor diamagnetic species.

    PubMed

    Nishio, Masaki; Miyasaka, Hitoshi

    2014-05-05

    The donor/acceptor ionic chain (i.e., the D(+)A(-) chain) [Ru2(2-MeO-4-ClPhCO2)4(BTDA-TCNQ)]·2.5(benzene) (1; 2-MeO-4-ClPhCO2(-) = 2-methoxy-4-chlorobenzoate; BTDA-TCNQ = bis(1,2,5-thiadiazolo)tetracyanoquinodimethane) is a ferrimagnetic chain with S = 3/2 from [Ru2(II,III)](+) (i.e., D(+)) and S = 1/2 from BTDA-TCNQ(•-) (i.e., A(-)), with J ≈ -100 K, in which long-range antiferromagnetic ordering at TN = 11 K occurs because interchain antiferromagnetic interactions are critical. Compound 1 undergoes a reversible crystal-to-crystal structural transformation with the elimination/absorption of the crystallization solvent to form the dried compound [Ru2(2-MeO-4-ClPhCO2)4(BTDA-TCNQ)] (1'), which has a higher TN (14 K). This change is clearly caused by the shortening of the interchain distances because the exchange coupling parameter for the chain is the same in both 1 and 1'. The chain compounds in 1 can be doped with minor diamagnetic [Rh2(II,II)] species, [{(Ru2)(1-x)(Rh2)(x)(2-MeO-4-ClPhCO2)4}(BTDA-TCNQ)]·2.5(benzene) (x = 0.03 for Rh-3%; x = 0.05 for Rh-5%; x = 0.16 for Rh-16%), which shifts the TN to lower temperatures, the magnitude of the shift being dependent on the doping ratio x (TN = 5.9 K for Rh-3%, TN = 3.7 K for Rh-5%, and TN was not observed above 1.8 K for Rh-16%). Drying a doped compound increased its TN, as was found for 1': TN = 9.9 K for Rh-3%', TN = 9.2 K for Rh-5%', and TN was not observed above 1.8 K for Rh-16%'. TN had a linear relationship with the doping ratio x of the [Rh2] species in both the fresh and dried compounds. The TN linear relationship is associated with the magnitude of the effective magnetic dipole (i.e., the average correlation length) in the chains caused by the [Rh2] defects as well as naturally generated defects in the synthetic process and with the interchain distances affected by the crystal-to-crystal transformations. These results demonstrate that slightly modifying the short-range correlation lengths, which changes

  19. Photoresponse of 60Ni below 10-MeV excitation energy: Evolution of dipole resonances in fp-shell nuclei near N=Z

    NASA Astrophysics Data System (ADS)

    Scheck, M.; Ponomarev, V. Yu.; Fritzsche, M.; Joubert, J.; Aumann, T.; Beller, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Raut, R.; Romig, C.; Rusev, G.; Savran, D.; Schorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.

    2013-10-01

    Background: Within the last decade, below the giant dipole resonance the existence of a concentration of additional electric dipole strength has been established. This accumulation of low-lying E1 strength is commonly referred to as pygmy dipole resonance (PDR).Purpose: The photoresponse of 60Ni has been investigated experimentally and theoretically to test the evolution of the PDR in a nucleus with only a small neutron excess. Furthermore, the isoscalar and isovector M1 resonances were investigated.Method: Spin-1 states were excited by exploiting the (γ,γ') nuclear resonance fluorescence technique with unpolarized continuous bremsstrahlung as well as with fully linearly polarized, quasimonochromatic, Compton-backscattered laser photons in the entrance channel of the reaction.Results: Up to 10 MeV a detailed picture of J=1 levels was obtained. For the preponderant number of the individual levels spin and parity were firmly assigned. Furthermore, branching ratios, transition widths, and reduced B(E1) or B(M1) excitation probability were calculated from the measured scattering cross sections. A comparison with theoretical results obtained within the quasiparticle phonon model allows an insight into the microscopic structure of the observed states.Conclusions: Below 10 MeV the directly observed E1 strength [∑B(E1)↑=(153.8±9.5) e2(fm)2] exhausts 0.5% of the Thomas-Reiche-Kuhn sum rule. This value increases to 0.8% of the sum rule [∑B(E1)↑=(250.9±31.1) e2(fm)2] when indirectly observed branches to lower-lying levels are considered. Two accumulations of M1 excited spin-1 states near 8 and 9 MeV excitation energy are identified as isoscalar and isovector M1 resonances dominated by proton and neutron f7/2→f5/2 spin-flip excitations. The B(M1)↑ strength of these structures accumulates to 3.94(27)μN2.

  20. Generation of auroral kilometric radiation by a finite-size source in a dipole magnetic field

    NASA Astrophysics Data System (ADS)

    Burinskaya, T. M.; Shevelev, M. M.

    2016-10-01

    Generation, amplification, and propagation of auroral kilometric radiation in a narrow three-dimensional plasma cavity in which a weakly relativistic electron beam propagates is studied in the geometrical optics approximation. It is shown that the waves that start with a group velocity directed earthward and have optimal relation between the wave vector components determining the linear growth rate and the wave residence time inside the amplification region undergo the largest amplification. Taking into account the longitudinal velocity of fast electrons results in the shift of the instability domain toward wave vectors directed to the Earth and leads to a change in the dispersion relation, due to which favorable conditions are created for the generation of waves with frequencies above the cutoff frequency for the cold background plasma at the wave generation altitude. The amplification factor for these waves is lower than for waves that have the same wave vectors but are excited by the electron beams with lower velocities along the magnetic field. For waves excited at frequencies below the cutoff frequency of the background plasma at the generation altitude, the amplification factor increases with increasing longitudinal electron velocity, because these waves reside for a longer time in the amplification region.

  1. Double excitations and state-to-state transition dipoles in π-π∗ excited singlet states of linear polyenes: Time-dependent density-functional theory versus multiconfigurational methods

    NASA Astrophysics Data System (ADS)

    Mikhailov, Ivan A.; Tafur, Sergio; Masunov, Artëm E.

    2008-01-01

    The effect of static and dynamic electron correlation on the nature of excited states and state-to-state transition dipole moments is studied with a multideterminant wave function approach on the example of all-trans linear polyenes ( C4H6 , C6H8 , and C8H10 ). Symmetry-forbidden singlet nAg states were found to separate into three groups: purely single, mostly single, and mostly double excitations. The excited-state absorption spectrum is dominated by two bright transitions: 1Bu-2Ag and 1Bu-mAg , where mAg is the state, corresponding to two-electron excitation from the highest occupied to lowest unoccupied molecular orbital. The richness of the excited-state absorption spectra and strong mixing of the doubly excited determinants into lower- nAg states, reported previously at the complete active space self-consistent field level of theory, were found to be an artifact of the smaller active space, limited to π orbitals. When dynamic σ-π correlation is taken into account, single- and double-excited states become relatively well separated at least at the equilibrium geometry of the ground state. This electronic structure is closely reproduced within time-dependent density-functional theory (TD DFT), where double excitations appear in a second-order coupled electronic oscillator formalism and do not mix with the single excitations obtained within the linear response. An extension of TD DFT is proposed, where the Tamm-Dancoff approximation (TDA) is invoked after the linear response equations are solved (a posteriori TDA). The numerical performance of this extension is validated against multideterminant-wave-function and quadratic-response TD DFT results. It is recommended for use with a sum-over-states approach to predict the nonlinear optical properties of conjugated molecules.

  2. Magnetic Excitations in the Nearly Localized, Itinerant Magnet Gd, Studied by Neutron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Graroth, G. E.; Aczel, A. A.; Fernandez-Baca, J. A.; Nagler, S. E.

    2012-02-01

    Many of the current questions about magnetic superconductors are present when these complex materials are in the normal state. Therefore studies of simpler itinerant magnets may help provide understanding of these phenomena. We chose to study an Itinerant magnet near to the fully localized limit. The system of choice, Gd has a total moment size of ˜7.6 μB of which ˜0.6μB of that is itinerant. We used the SEQUOIA spectrometer, at the Spallation Neutron Source at Oak Ridge National Laboratory, to measure the magnetic excitations in a 12 gm ^160Gd single crystal. The fine resolution Fermi chopper was spun at 360 Hz and phased for Ei = 50 meV. The crystal was mounted with the h0l plane horizontal and then rotated around the vertical axis in 1^o steps. This method, and the large out of plane detector coverage of SEQUOIA, provided continuous coverage of a large region of reciprocal space allowing us to map the magnetic excitations. This map provides a measured structure factor for comparison to spin wave models with and without itinerancy effects. There measurements also more clearly resolve the excitations along the h00 direction than in previous studies (J. W. Cable, R. M. Nicklow and N. Wakabayashi Phys. Rev. B 32, 1710 (1985)).

  3. 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.

  4. 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.

  5. Magnetic rotation phenomenon in the dipole (Δ I = 1) bands of transitional strontium (Sr) isotopes near N=50 shell closure

    NASA Astrophysics Data System (ADS)

    Kumar, Naveen; Kumar, S.; Mandal, S. K.; Saha, S.; Sethi, J.; Palit, R.

    2017-02-01

    The lifetime measurements were done for the transitions of the dipole (Δ I=1) bands in 85,86Sr nuclei using the Doppler Shift Attenuation Method (DSAM). The high-spin states in these nuclei were populated in the 76Ge(13C, 4n)85Sr and 76Ge(13C, 3n)86Sr reactions. The B( M1) transition rates have been obtained for the states of two positive-parity dipole (Δ I=1) bands in the 85Sr nucleus and one positive-parity dipole (Δ I=1) band in the 86 Sr nucleus. The present results on the transition rates are important to know whether these dipole (Δ I=1) bands have the signatures of Magnetic Rotation (MR). In order to investigate their magnetic character, the experimental results have been compared with the calculations within the framework of hybrid Tilted-Axis-Cranking (TAC) model. On the basis of the TAC calculations, band 2 of the 85Sr nucleus is assigned the π (g_{9/2})2⊗ ν (g_{9/2})^{-1} configuration and shows the MR character, while for band 3, the π [(g_{9/2})2 (f_{5/2})2]⊗ ν (g_{9/2})^{-1} configuration is suggested. In the case of 86Sr nucleus, band 3 has the π (g_{9/2})2⊗ ν (g_{9/2})^{-2} configuration below the spin I^{π} = 16+ and above this spin the π [(g_{9/2})2 (f_{5/2})1 (p_{1/2}/p_{3/2})1] ⊗ ν (g_{9/2})^{-2} configuration plays an important role. The experimental B( M1) transition rates show a decreasing trend with the increase in spin and are comparable with the TAC calculations before the I^{π} = 16+.

  6. Extremely long-lived magnetic excitations in supported Fe chains

    NASA Astrophysics Data System (ADS)

    Gauyacq, J. P.; Lorente, N.

    2016-07-01

    We report on a theoretical study of the lifetime of the first excited state of spin chains made of an odd number of Fe atoms on C u2N /Cu (100 ) . Yan, Choi, Burgess, Rolf-Pissarczyk, and Loth [Nat. Nanotech. 10, 40 (2015), 10.1038/nnano.2014.281] recently observed very long lifetimes in the case of F e3 chains. We consider the decay of the first excited state induced by electron-hole pair creation in the substrate. For a finite magnetic field, the two lowest-lying states in the chain have a quasi-Néel state structure. Decay from one state to the other strongly depends on the degree of entanglement of the local spins in the chain. The weak entanglement in the chain accounts for the long lifetimes that increase exponentially with chain length. Despite their apparently very different properties, the behavior of odd and even chains is governed by the same kind of phenomena, in particular entanglement effects. The present results account quite well for the lifetimes recently measured by Yan et al. on F e3 .

  7. Permanent Magnet Synchronous Condenser with Solid State Excitation

    SciTech Connect

    Hsu, Ping; Muljadi, Eduard; Wu, Ziping; Gao, Wenzhong

    2015-10-05

    A synchronous condenser consists of a free-spinning wound-field synchronous generator and a field excitation controller. In this paper, we propose a synchronous generator that employs a permanent magnet synchronous generator (PMSG) instead of a wound-field machine. PMSGs have the advantages of higher efficiency and reliability. In the proposed configuration, the reactive power control is achieved by a voltage source converter connected in series with the PMSG and the grid. The converter varies the phase voltage of the PMSG so as to create the same effect of over or under excitation in a wound-field machine. The converter output voltage level controls the amount and the direction of the produced reactive power and the voltage's phase is kept in-phase with the grid voltage except a slight phase can be introduced so that some power can be drawn from the grid for maintaining the DC bus voltage level of the converter. Since the output voltage of the converter is only a fraction of the line voltage, its VA rating is only a fraction of the rating of the PMSG. The proposed scheme is shown to be effective by computer simulation.

  8. Model of the Radio Frequency (RF) Excitation Response from Monopole and Dipole Antennas in a Large Scale Tank

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey D.; Zimmerli, Gregory A.

    2012-01-01

    Good antenna-mode coupling is needed for determining the amount of propellant in a tank through the method of radio frequency mass gauging (RFMG). The antenna configuration and position in a tank are important factors in coupling the antenna to the natural electromagnetic modes. In this study, different monopole and dipole antenna mounting configurations and positions were modeled and responses simulated in a full-scale tank model with the transient solver of CST Microwave Studio (CST Computer Simulation Technology of America, Inc.). The study was undertaken to qualitatively understand the effect of antenna design and placement within a tank on the resulting radio frequency (RF) tank spectrum.

  9. Excitation of Oscillations in the Magnetic Network on the Sun.

    PubMed

    Hasan; Kalkofen; van Ballegooijen AA

    2000-05-20

    We examine the excitation of oscillations in the magnetic network of the Sun through the footpoint motion of photospheric magnetic flux tubes located in intergranular lanes. The motion is derived from a time series of high-resolution G-band and continuum filtergrams using an object-tracking technique. We model the response of the flux tube to the footpoint motion in terms of the Klein-Gordon equation, which is solved analytically as an initial value problem for transverse (kink) waves. We compute the wave energy flux in upward-propagating transverse waves. In general we find that the injection of energy into the chromosphere occurs in short-duration pulses, which would lead to a time variability in chromospheric emission that is incompatible with observations. Therefore, we consider the effects of turbulent convective flows on flux tubes in intergranular lanes. The turbulent flows are simulated by adding high-frequency motions (periods 5-50 s) with an amplitude of 1 km s(-1). The latter are simulated by adding random velocity fluctuations to the observationally determined velocities. In this case, we find that the energy flux is much less intermittent and can in principle carry adequate energy for chromospheric heating.

  10. Modulation of motor cortex excitability by peripheral magnetic stimulation of different stimulus sites and frequencies.

    PubMed

    Sato, A; Liu, X; Torii, T; Iwahashi, M; Iramina, K; Sato, A; Liu, X; Torii, T; Iwahashi, M; Iramina, K; Iwahashi, M; Liu, X; Sato, A; Iramina, K; Torii, T

    2016-08-01

    Peripheral stimulation is known to influence the state of cortical excitability. The purpose of this study is to investigate whether peripheral magnetic stimulation has similar effects on cortical excitability to transcranial magnetic stimulation (TMS). A magnetic stimulator with a flat figure-of-eight coil was used for both TMS, and peripheral magnetic stimulation applied to the bilateral forearms. TMS was performed on the left primary motor cortex to evaluate influence of the peripheral magnetic stimulation, and motor evoked potential (MEP) was measured from the right first dorsal interosseous. Peripheral magnetic stimulation was performed at a stimulus frequency of 1 Hz or 10 Hz, to the stimulus sites on the right and left supination of the forearm. The effects of peripheral magnetic stimulation were evaluated by comparing the mean MEP amplitude elicited by TMS before and after peripheral magnetic stimulation. We found that cortical excitability varied according to the stimulation site and frequency of the peripheral magnetic stimulation. The inhibition of cortical excitability was observed following 1 Hz peripheral magnetic stimulation over the right forearm (p<;0.001). In contrast, increased cortical excitability was observed using 1 Hz peripheral magnetic stimulation over the left forearm and 10 Hz stimulation over either the right or left forearms. We suggest that peripheral magnetic stimulation has a similar effect to TMS, and can induce both facilitation and inhibition of cortical excitability.

  11. Self-assembly of three-dimensional ensembles of magnetic particles with laterally shifted dipoles.

    PubMed

    Yener, Arzu B; Klapp, Sabine H L

    2016-02-21

    We consider a model of colloidal spherical particles carrying a permanent dipole moment which is laterally shifted out of the particles' geometrical centres, i.e. the dipole vector is oriented perpendicular to the radius of the particles. Varying the shift δ from the centre, we analyse ground state structures for two, three and four hard spheres, using a simulated annealing procedure. We also compare earlier ground state results. We then consider a bulk system at finite temperatures and different densities. Using molecular dynamics simulations, we examine the equilibrium self-assembly properties for several shifts. Our results show that the shift of the dipole moment has a crucial impact on both the ground state configurations as well as the self-assembled structures at finite temperatures.

  12. Hour-glass magnetic excitations induced by nanoscopic phase separation in cobalt oxides

    NASA Astrophysics Data System (ADS)

    Drees, Y.; Li, Z. W.; Ricci, A.; Rotter, M.; Schmidt, W.; Lamago, D.; Sobolev, O.; Rütt, U.; Gutowski, O.; Sprung, M.; Piovano, A.; Castellan, J. P.; Komarek, A. C.

    2014-12-01

    The magnetic excitations in the cuprate superconductors might be essential for an understanding of high-temperature superconductivity. In these cuprate superconductors the magnetic excitation spectrum resembles an hour-glass and certain resonant magnetic excitations within are believed to be connected to the pairing mechanism, which is corroborated by the observation of a universal linear scaling of superconducting gap and magnetic resonance energy. So far, charge stripes are widely believed to be involved in the physics of hour-glass spectra. Here we study an isostructural cobaltate that also exhibits an hour-glass magnetic spectrum. Instead of the expected charge stripe order we observe nano phase separation and unravel a microscopically split origin of hour-glass spectra on the nano scale pointing to a connection between the magnetic resonance peak and the spin gap originating in islands of the antiferromagnetic parent insulator. Our findings open new ways to theories of magnetic excitations and superconductivity in cuprate superconductors.

  13. Hour-glass magnetic excitations induced by nanoscopic phase separation in cobalt oxides.

    PubMed

    Drees, Y; Li, Z W; Ricci, A; Rotter, M; Schmidt, W; Lamago, D; Sobolev, O; Rütt, U; Gutowski, O; Sprung, M; Piovano, A; Castellan, J P; Komarek, A C

    2014-12-23

    The magnetic excitations in the cuprate superconductors might be essential for an understanding of high-temperature superconductivity. In these cuprate superconductors the magnetic excitation spectrum resembles an hour-glass and certain resonant magnetic excitations within are believed to be connected to the pairing mechanism, which is corroborated by the observation of a universal linear scaling of superconducting gap and magnetic resonance energy. So far, charge stripes are widely believed to be involved in the physics of hour-glass spectra. Here we study an isostructural cobaltate that also exhibits an hour-glass magnetic spectrum. Instead of the expected charge stripe order we observe nano phase separation and unravel a microscopically split origin of hour-glass spectra on the nano scale pointing to a connection between the magnetic resonance peak and the spin gap originating in islands of the antiferromagnetic parent insulator. Our findings open new ways to theories of magnetic excitations and superconductivity in cuprate superconductors.

  14. Performance Prediction of a Hybrid-Excitation Synchronous Machine with Axially Arranged Excitation Poles and Permanent-Magnet Poles

    NASA Astrophysics Data System (ADS)

    Matsuuchi, Kotaro; Fukami, Tadashi; Naoe, Nobuyuki; Hanaoka, Ryoichi; Takata, Shinzo; Miyamoto, Toshio

    This paper presents a method of predicting the steady-state performance of a new hybrid-excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent-magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to iron core, is derived. Based on this equivalent circuit, the steady-state performance of the HESM is calculated, and the results are confirmed through experiments.

  15. Doping dependence of the magnetic excitations in La2−xSrxCuO4

    DOE PAGES

    Meyers, D.; Miao, H.; Walters, A. C.; ...

    2017-02-15

    The magnetic correlations within the cuprates have undergone intense scrutiny as part of efforts to understand high-temperature superconductivity. We explore the evolution of the magnetic correlations along the nodal direction of the Brillouin zone in La2–xSrxCuO4, spanning the doping phase diagram from the antiferromagnetic Mott insulator at x = 0 to the metallic phase at x = 0.26. Magnetic excitations along this direction are found to be systematically softened and broadened with doping, at a higher rate than the excitations along the antinodal direction. This phenomenology is discussed in terms of the nature of the magnetism in the doped cuprates.more » As a result, survival of the high-energy magnetic excitations, even in the overdoped regime, indicates that these excitations are marginal to pairing, while the influence of the low-energy excitations remains ambiguous.« less

  16. Doping dependence of the magnetic excitations in La2-xSrxCuO4

    DOE PAGES

    Meyers, D.; Miao, H.; Walters, A. C.; ...

    2017-02-15

    The magnetic correlations within the cuprates have undergone intense scrutiny as part of efforts to understand high-temperature superconductivity. We explore the evolution of the magnetic correlations along the nodal direction of the Brillouin zone in La2–xSrxCuO4, spanning the doping phase diagram from the antiferromagnetic Mott insulator at x = 0 to the metallic phase at x = 0.26. Magnetic excitations along this direction are found to be systematically softened and broadened with doping, at a higher rate than the excitations along the antinodal direction. This phenomenology is discussed in terms of the nature of the magnetism in the doped cuprates.more » As a result, survival of the high-energy magnetic excitations, even in the overdoped regime, indicates that these excitations are marginal to pairing, while the influence of the low-energy excitations remains ambiguous.« less

  17. Third-Scale Prototype of a Shielded Magnet for Measurement of the Electric Dipole Moment of the Neutron

    NASA Astrophysics Data System (ADS)

    Biswas, Aritra

    2015-10-01

    Discovery of an electric dipole moment in neutrons (nEDM) would be a novel instance of CP violation, with implications for extending the Standard Model and potentially helping explain matter-antimatter asymmetry. Experiments using shifts in polarized neutron spin-precession frequency to measure the nEDM are prone to a geometric phase (GP) effect, caused by gradients of the magnetic field, that can create a false signal. Preventing the GP effect requires precise engineering to create a space-uniform magnetic field. We present a third-scale prototype of a shielded magnet suitable for a more precise nEDM measurement, with improvements over earlier models. The field is produced by a cosθ coil wound with superconducting (SC) wire. Two cylindrical shields made of ferromagnetic Metglas and SC lead surround the magnet; the lead shield is closed on top and bottom with SC lead endcaps. An aluminum shell surrounds these components and serves as a vacuum chamber, cooling its interior to 4 K such that the coil wire and lead shield become SC. A cavity in this shell serves as a warm bore, allowing a magnetic probe to explore the field around fiducial volumes which will be used to measure the nEDM in the full-scale experiment. The magnetic field profile of this prototype is presented.

  18. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    DOE PAGES

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; ...

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the searchmore » for high temperature superconductivity in this system.« less

  19. Anisotropic softening of magnetic excitations in lightly electron-doped Sr2IrO4

    SciTech Connect

    Liu, X.; Dean, M. P. M.; Meng, Z. Y.; Upton, M. H.; Qi, T.; Gog, T.; Cao, Y.; Lin, J. Q.; Meyers, D.; Ding, H.; Cao, G.; Hill, J. P.

    2016-06-10

    The magnetic excitations in electron doped (Sr1-xLax)2IrO4 with x = 0:03 were measured using resonant inelastic X-ray scattering at the Ir L3-edge. Although much broadened, well defined dispersive magnetic excitations were observed. Comparing with the magnetic dispersion from the undoped compound, the evolution of the magnetic excitations upon doping is highly anisotropic. Along the anti-nodal direction, the dispersion is almost intact. On the other hand, the magnetic excitations along the nodal direction show significant softening. These results establish the presence of strong magnetic correlations in electron doped (Sr1-xLax)2IrO4 with close analogies to the hole doped cuprates, further motivating the search for high temperature superconductivity in this system.

  20. DESIGN OF AN AC-DIPOLE FOR USE IN RHIC.

    SciTech Connect

    PARKER,B.; BAI,M.; JAIN,A.; MCINTYRE,G.; METH,M.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.

    1999-03-29

    We present two options for implementing a pair of AC-dipoles in RHIC for spin flipping, measuring linear optical functions and nonlinear diagnostics. AC-dipoles are magnets that can be adiabatically excited and de-excited with a continuous sine-wave in order to coherently move circulating beam out to large betatron amplitudes without incurring emittance blow up [1]. The AGS already uses a similar device for getting polarized proton beams through depolarizing resonances [2]. By placing the magnets in the IP4 common beam region, two AC-dipoles are sufficient to excite both horizontal and vertical motion in both RHIC rings. While we initially investigated an iron-dominated magnet design using available steel tape cores; we now favor a new air coil plus ferrite design featuring mechanical frequency tuning, in order to best match available resources to demanding frequency sweeping requirements. Both magnet designs are presented here along with model magnet test results. The challenge is to make AC-dipoles available for year 2000 RHIC running.

  1. Solvent effect on absorption and fluorescence spectra of three biologically active carboxamides (C1, C2 and C3). Estimation of ground and excited state dipole moment from solvatochromic method using solvent polarity parameters.

    PubMed

    Patil, N R; Melavanki, R M; Kapatkar, S B; Ayachit, N H; Saravanan, J

    2011-05-01

    The absorption and fluorescence spectra of three Carboxamides namely (E)-2-(4-Chlorobenzylideneamino)-N-(2-chlorophenyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (C(1)), (E)-N-(3-Chlorophenyl)-2-(3, 4-dimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (C(2)) and (E)-N-(3-Chlorophenyl)-2-(3,4,5-trimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (C(3)) have been recorded at room temperature in solvents of different polarities using dielectric constant (ε) and refractive index (n). Experimental ground (μ(g)) and excited (μ(e)) state dipole moments are estimated by means of solvatochromic shift method and also the excited dipole moments are estimated in combination with ground state dipole moments. It was estimated that dipole moments of the excited state were higher than those of the ground state of all three molecules. Further, the changes in dipole moment (Δμ) were calculated both from solvatochromic shift method and on the basis of microscopic empirical solvent polarity parameter (E(N)(T)) and the values are compared.

  2. Permanent Magnet Synchronous Condenser with Solid State Excitation: Preprint

    SciTech Connect

    Hsu, P.; Muljadi, E.; Wu, Z.; Gao, W.

    2015-04-07

    A typical synchronous condenser (SC) consists of a free-spinning, wound-field synchronous generator and a field excitation controller. In this paper, we propose an SC that employs a permanent magnet synchronous generator (PMSG) instead of a wound-field machine. PMSGs have the advantages of higher efficiency and reliability. In the proposed configuration, the reactive power control is achieved by a voltage converter controller connected in series to the PMSG. The controller varies the phase voltage of the PMSG and creates the same effect on the reactive power flow as that of an over- or underexcited wound-field machine. The controller’s output voltage magnitude controls the amount of the reactive power produced by the SC. The phase of the controller’s output is kept within a small variation from the grid voltage phase. This small phase variation is introduced so that a small amount of power can be drawn from the grid into the controller to maintain its DC bus voltage. Because the output voltage of the controller is only a fraction of the line voltage, its VA rating is only a fraction of the rating of the PMSG. The proposed scheme is shown to be effective by computer simulations.

  3. Thermal and structural performance of a single tube support post for the Superconducting Super Collider dipole magnet cryostat

    SciTech Connect

    Boroski, W.N.; Nicol, T.H.; Ruschman, M.K.; Schoo, C.J.

    1993-07-01

    The reentrant support post currently incorporated in the Superconducting Super Collider (SSC) dipole cryostat has been shown to meet the structural and thermal requirements of the cryostat, both in prototype magnet assemblies and through component testing. However, the reentrant post design has two major drawbacks: tight dimensional control on all components, and cost driven by these tolerance constraints and a complex assembly procedure. A single tube support post has been developed as an alternative to the reentrant post design. Several prototype assemblies have been fabricated and subjected to structural testing. Compressive, tensile, and bending forces were applied to each assembly with deflection measured at several locations. A prototype support post has also been thermally evaluated in a heat leak measurement facility. Heat load to 4.2 K was measured with the intermediate post intercept operating at various temperatures while thermometers positioned along the conductive path of the post mapped thermal gradients. Results from these measurements indicate the single tube support post meets the design criteria for the SSC dipole magnet cryostat support system.

  4. 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.

  5. Limits on the monopole polarization magnetic field from measurements of the electric dipole moments of atoms, molecules, and the neutron

    NASA Astrophysics Data System (ADS)

    Flambaum, V. V.

    1997-03-01

    A radial magnetic field can induce a time-invariance-violating electric-dipole moment (EDM) in quantum systems. The EDMs of the Tl, Cs, Xe, and Hg atoms and the neutron that are produced by such a field are estimated. The contributions of such a field to the constants, χ of the T, P-odd interactions χeN.s/s and χNN.I/I are also estimated for the TlF, HgF, and YbF molecules [where s (I) is the electron (nuclear) spin and N is the molecular axis]. The best limit on the contact monopole field can be obtained from the measured value of the Tl EDM. The possibility of such a field being produced from polarization of the vacuum of electrically charged magnetic monopoles (dyons) by a Coulomb field is discussed, as well as the limit on these dyons. An alternative mechanism involves chromomagnetic and chromoelectric fields in QCD.

  6. DQ-DRENAR: A new NMR technique to measure site-resolved magnetic dipole-dipole interactions in multispin-1/2 systems: Theory and validation on crystalline phosphates

    NASA Astrophysics Data System (ADS)

    Ren, Jinjun; Eckert, Hellmut

    2013-04-01

    A new solid state NMR technique is described for measuring homonuclear dipole-dipole interactions in multi-spin-1/2 systems under magic-angle spinning conditions. Re-coupling is accomplished in the form of an effective double quantum (DQ) Hamiltonian created by a symmetry-based POST-C7 sequence consisting of two excitation blocks, attenuating the signal (intensity S'). For comparison, a reference signal S0 with the dipolar re-coupling absent is generated by shifting the phase of the second block by 90° relative to the first block. As in rotational echo double resonance, the homonuclear dipole-dipole coupling constant can then be extracted from a plot of the normalized difference signal (S0 - S')/S0 versus dipolar mixing time. The method is given the acronym DQ-DRENAR ("Double-Quantum-based Dipolar Re-coupling effects Nuclear Alignment Reduction"). The method is analyzed mathematically, and on the basis of detailed simulations, with respect to the order and the geometry of the spin system, the dipolar truncation phenomenon, and the influence of the chemical shift anisotropy on experimental curves. Within the range of (S0 - S')/S0 ≤0.3-0.5 such DRENAR curves can be approximated by simple parabolae, yielding effective squared dipole-dipole coupling constants summed over all the pairwise interactions present. The method has been successfully validated for 31P-31P distance determinations of numerous crystalline model compounds representing a wide range of dipolar coupling strengths.

  7. In-orbit offline estimation of the residual magnetic dipole biases of the POPSAT-HIP1 nanosatellite

    NASA Astrophysics Data System (ADS)

    Seriani, S.; Brama, Y. L.; Gallina, P.; Manzoni, G.

    2016-05-01

    The nanosatellite POPSAT-HIP1 is a Cubesat-class spacecraft launched on the 19th of June 2014 to test cold-gas based micro-thrusters; it is, as of April 2015, in a low Earth orbit at around 600 km of altitude and is equipped, notably, with a magnetometer. In order to increment the performance of the attitude control of nanosatellites like POPSAT, it is extremely useful to determine the main biases that act on the magnetometer while in orbit, for example those generated by the residual magnetic moment of the satellite itself and those originating from the transmitter. Thus, we present a methodology to perform an in-orbit offline estimation of the magnetometer bias caused by the residual magnetic moment of the satellite (we refer to this as the residual magnetic dipole bias, or RMDB). The method is based on a genetic algorithm coupled with a simplex algorithm, and provides the bias RMDB vector as output, requiring solely the magnetometer readings. This is exploited to compute the transmitter magnetic dipole bias (TMDB), by comparing the computed RMDB with the transmitter operating and idling. An experimental investigation is carried out by acquiring the magnetometer outputs in different phases of the spacecraft life (stabilized, maneuvering, free tumble). Results show remarkable accuracy with an RMDB orientation error between 3.6 ° and 6.2 ° , and a module error around 7 % . TMDB values show similar coherence values. Finally, we note some drawbacks of the methodologies, as well as some possible improvements, e.g. precise transmitter operations logging. In general, however, the methodology proves to be quite effective even with sparse and noisy data, and promises to be incisive in the improvement of attitude control systems.

  8. Polarization-Dependent Interference of Coherent Scattering from Orthogonal Dipole Moments of a Resonantly Excited Quantum Dot

    NASA Astrophysics Data System (ADS)

    Chen, Disheng; Lander, Gary R.; Solomon, Glenn S.; Flagg, Edward B.

    2017-01-01

    Resonant photoluminescence excitation (RPLE) spectra of a neutral InGaAs quantum dot show unconventional line shapes that depend on the detection polarization. We characterize this phenomenon by performing polarization-dependent RPLE measurements and simulating the measured spectra with a three-level quantum model. The spectra are explained by interference between fields coherently scattered from the two fine structure split exciton states, and the measurements enable extraction of the steady-state coherence between the two exciton states.

  9. Current distribution in parallel paths of the coils of a 50 Hz prototype dipole magnet

    SciTech Connect

    Otter, A.J.

    1996-07-01

    The prototype dipole made for TRIUMF`s Kaon Factory proposal used coils with 12 parallel paths to reduce eddy current losses in the conductors. The ac current distribution in these paths was non-uniform due to different self and mutual inductances. Small differences in inductance can cause large circulating currents in the parallel windings. This paper describes the measurement of the inductances and shows an attempt to predict the current distribution for two alternative connection schemes.

  10. Simple estimation of dipole source z-distance with compact magnetic gradiometer

    NASA Astrophysics Data System (ADS)

    Janošek, M.; Platil, A.; Vyhnánek, J.

    2016-03-01

    A compact magnetometer/gradiometer with combined homogeneous and gradient outputs facilitates precise measurement of both H and G values with good spatial and temporal coherence. By evaluating combination of both signals, it is possible to estimate distance to a dipole source with relatively small error and largely independent from precise knowledge of source strength, orientation and lateral displacement. The performance is limited primarily by ambient noise. With an AC-driven source, tool navigation or distance sensing is also possible.

  11. The excited state dipole moments of betaine pyridinium investigated by an innovative solvatochromic analysis and TDDFT calculations.

    PubMed

    Pawlowska, Zuzanna; Lietard, Aude; Aloïse, Stéphane; Sliwa, Michel; Idrissi, Abdenacer; Poizat, Olivier; Buntinx, Guy; Delbaere, Stéphanie; Perrier, Aurélie; Maurel, François; Jacques, Patrice; Abe, Jiro

    2011-08-07

    This work reports on the solvatochromic properties of a simple heterocyclic betaine pyridinium, 2-(1-pyridinio)benzimidazolate (SBPa), having promising potentialities in non-linear optics. From advanced PCM-TDDFT calculations, the solvatochromism of SBPa was found to be unusual, involving two different electronic states for absorption (S(0)→ S(2)) and emission (S(1)→S'(0)). To account for this behavior, we developed an innovative physical treatment which consists in a non-linear fit of the solvatochromic data using the Bilot-Kawski theoretical model and visualizing the least-square coefficient χ(2) on a 2D map as a function of the solute polarizability and gas phase absorption energy. In parallel, Kamlet-Taft correlations were undertaken to select a propitious set of electrostatic solvents usable in this treatment. Protic solvents that lead to specific interactions and nonpolar solvents that favor dimerization processes were excluded. From a choice of aprotic solvents with sufficiently high polarity, 4 dipole moments μ(g)(S(0)) = +9.1 D, μ(e)(S(2)) = -1.5 D, μ(e)(S(1)) = 0 D and μ(g)(S'(0)) = +3.31 D were determined, the 3 former values being in close agreement with TDDFT values, although the solute polarizability values seem underestimated. Anyhow, disregarding this discrepancy, we evaluated the static hyperpolarizability to β(0) = -64 × 10(-30) esu from the solvatochromic data in close agreement with DFT calculations.

  12. A quantitative study of the effect of solvent on the electronic absorption and fluorescence spectra of substituted phenothiazines: evaluation of their ground and excited singlet-state dipole moments

    NASA Astrophysics Data System (ADS)

    Párkányi, C.; Boniface, C.; Aaron, J. J.; Maafi, M.

    1993-11-01

    Electronic absorption and fluorescence excitation and emission spectra of five phenothiazines (phenothiazine, promethazine, thionine, methylene blue and Azure A) were determined at room temperature (293 K) in several solvents of various polarities (cyclohexane, dioxane, ethyl ether, chloroform, ethyl acetate, 1-butanol, 2-propanol, ethanol, methanol, acetonitrile, dimethylformamide and dimethyl sulfoxide). The effect of the solvents upon the spectral characteristics was studied. In combination with the ground state dipole moments of these phenothiazines, the spectral data were used to evaluate their first excited singlet-state dipole moments by means of the solvatochromic shift method (Bakhshiev's and Kawski—Chamma—Viallet correlations). The theoretical ground and excited singlet-state dipole moments for phenothiazines were calculated as a vector sum of the π component (obtained by the Pariser—Parr—Pople method) and the σ component (obtained from σ-bond moments). A reasonable agreement was found with the experimental values. For most phenothiazines under study, excited singlet-state dipole moments were found to be significantly higher than their ground-state counterparts. The application of the Kamlet—Abboud—Taft solvatochromic parameters to the solvent effect on spectral properties of phenothiazines is discussed.

  13. Magnetic-dipole-to-electric-quadrupole cross-susceptibilities for relativistic hydrogenlike atoms in some low-lying discrete energy eigenstates

    NASA Astrophysics Data System (ADS)

    Stefańska, Patrycja

    2017-01-01

    In this paper we present tabulated data for magnetic-dipole-to-electric-quadrupole cross-susceptibilities (χ M 1 →E 2) for Dirac one-electron atoms with a pointlike, spinless and motionless nucleus of charge Ze. Numerical values of this susceptibility for the hydrogen atom (Z = 1) and for hydrogenic ions with 2 ⩽ Z ⩽ 137 are computed from the general analytical formula, recently derived by us (Stefanska, 2016), valid for an arbitrary discrete energy eigenstate. In this work we provide 30 tables with the values of χ M 1 →E 2 for the ground state, and also for the first, the second and the third set of excited states (i.e.: 2s1/2, 2p1/2, 2p3/2, 3s1/2, 3p1/2, 3p3/2, 3d3/2, 3d5/2, 4s1/2, 4p1/2, 4p3/2, 4d3/2, 4d5/2, 4f5/2 and 4f7/2) of the relativistic hydrogenlike atoms. The value of the inverse of the fine-structure constant used in the calculations is α-1 = 137.035999139, and was taken from CODATA 2014.

  14. Magnetic Dipole Moment Measurements of Picosecond States in Even and Odd Heavy Nuclei

    NASA Astrophysics Data System (ADS)

    Ballon, Douglas Jude

    The perturbed angular correlation and transient field technique is used to measure the precession of nuclear magnetic moments of low lying excited states in isotopes of silver, neodymium, samarium, and gadolinium. The precession measurements are used to explore three main areas of study. First, from the measurements made on ('150)Sm traversing gadolinium targets, the temperature dependence of the transient hyperfine field is deduced at ('150)Sm nuclei traveling at 2 < v/v(,0) < 4. These are compared with similar measurements made using iron targets. Second, the deduced values of the g-factors of the 2(,1)('+) states in even neodymium, samarium and gadolinium isotopes are discussed in connection with a possible proton shell closure at Z = 64. Third, the deduced values of the g-factors of the 3/2(,1)('-) and 5/2(,1)('-) states of ('107,109)Ag are compared to various theoretical predictions in order to explore any simple relationships that may exist between these states and the first 2(,1)('+) states of neighboring even-even nuclei. The following is a list of g-factors that were measured during the course of this work: (UNFORMATTED TABLE FOLLOWS). g(('107)Ag, 3/2(,1)('-)) = 0.607 (119). g(('109)Ag, 3/2(,1)('-)) = 0.661 (105). g(('107)Ag, 5/2(,1)('-)) = 0.409 (66). g(('109)Ag, 5/2(,1)('-)) = 0.287 (57). g(('144)Nd, 2(,1)('+)) = 0.166 (41). g(('146)Nd, 2(,1)('+)) = 0.312 (49). g(('148)Nd, 2(,1)('+)) = 0.411 (42). g(('150)Nd,2(,1)('+)) = 0.418 (38). g(('148)Sm, 2(,1)('+)) = 0.301 (33). g(('150)Sm, 2(,1)('+)) = 0.381 (27). g(('152)Gd, 2(,1)('+)) = 0.444 (40). (TABLE ENDS). The results of the temperature dependence experiment show deviations from an earlier measurement made using thulium in iron. The g-factors measured in the lighter isotopes of neodymium and samarium are significantly below the collective Z/A value. Fair agreement with the data can be obtained if proton shell closure is assumed at Z = 64 for N < 88. The measured g-factors in the silver isotopes

  15. 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.

  16. 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.

  17. Tevatron AC dipole system

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  18. Improvement of microwave feeding on a large bore ECRIS with permanent magnets by using coaxial semi-dipole antenna

    SciTech Connect

    Kurisu, Yosuke; Sakamoto, Naoki; Kiriyama, Ryutaro; Takenaka, Tomoya; Nozaki, Dai; Yano, Keisuke; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2012-11-06

    We are constructing a tandem type electron cyclotron resonance (ECR) ion source (ECRIS). The first stage of this ECRIS has a large-bore with cylindrically comb-shaped permanent magnets. 2.45GHz and 11-13GHz microwaves can be supplied individually and simultaneously to the plasma chamber. For 2.45GHz, a coaxial semi-dipole antenna is used to feed the microwaves. In previous experiments, there were two problems encountered when running the 2.45GHz microwaves. High incident power was necessary to keep ECR discharge at low operating pressure because of high reflected microwave power. The surface of a support insulator between the inner and the outer electrodes of coaxial semi-dipole antenna was easily metalized by sputtering of the metal wall inside the chamber. The purpose of this study was to solve these problems. Performing several simulation experiments supports the hypothesis that the position of the support insulator is significant for microwave power efficiency. The end result was the ability to sustain ECR discharges at extremely low incident microwave power, several tens of watts, by optimized matching of the position and shape of the insulator.

  19. Air-cooled trim dipoles for the Fermilab Main Injector

    SciTech Connect

    Harding, D. J.; Chester, N. S.; Garvey, J. D.; Krafczyk, G. E.; Makarov, A. I.; Terechkine, I.; Yarba, V. A.

    1997-05-01

    New horizontal and vertical trim dipoles have been designed for the Fermilab Main Injector (FMI) and are being assembled in the Fermilab Technical Division. Magnets are 42.6 cm in length (30.5 cm steel length) and have similar cross-section dimensions. The horizontal (vertical) magnet gap is 50.8 mm (127 mm) and the target integrated strength is 0.072 T*m (0.029 T*m). The major design effort lay in making air cooling possible for these magnets. This report presents the magnets` thermal and magnetic properties and discusses the limitation on excitation current.

  20. Interference effect in the dipole and nondipole anisotropy parameters of the Kr 4p photoelectrons in the vicinity of the Kr (3d){sup -1{yields}}np resonant excitations

    SciTech Connect

    Ricz, S.; Ricsoka, T.; Holste, K.; Borovik, A. Jr.; Bernhardt, D.; Schippers, S.; Mueller, A.; Koever, A.; Varga, D.

    2010-04-15

    The angular distribution of the Kr 4p photoelectrons was investigated in the photon energy range of the (3d){sup -1{yields}}np resonant excitations. The experimental dipole ({beta}) and nondipole ({gamma} and {delta}) anisotropy parameters were determined for the spin-orbit components of the Kr 4p shell. A simple theoretical model was developed for the description of the photoionization and excitation processes. An interference effect was observed between the direct photoionization and the resonant excitation participator Auger decay processes in the photon energy dependence of the experimental anisotropy parameters.

  1. 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.

  2. MAGNETIC BRAKING FORMULATION FOR SUN-LIKE STARS: DEPENDENCE ON DIPOLE FIELD STRENGTH AND ROTATION RATE

    SciTech Connect

    Matt, Sean P.; Pinsonneault, Marc H.; Greene, Thomas P. E-mail: kmac@ucar.edu E-mail: thomas.p.greene@nasa.gov

    2012-08-01

    We use two-dimensional axisymmetric magnetohydrodynamic simulations to compute steady-state solutions for solar-like stellar winds from rotating stars with dipolar magnetic fields. Our parameter study includes 50 simulations covering a wide range of relative magnetic field strengths and rotation rates, extending from the slow- and approaching the fast-magnetic-rotator regimes. Using the simulations to compute the angular momentum loss, we derive a semi-analytic formulation for the external torque on the star that fits all of the simulations to a precision of a few percent. This formula provides a simple method for computing the magnetic braking of Sun-like stars due to magnetized stellar winds, which properly includes the dependence on the strength of the magnetic field, mass loss rate, stellar radius, surface gravity, and spin rate, and which is valid for both slow and fast rotators.

  3. About a peculiar extra U(1): Z{sup '} discovery limit, muon anomalous magnetic moment, and electron electric dipole moment

    SciTech Connect

    Heo, Jae Ho

    2009-08-01

    The model (Lagrangian) with a peculiar extra U(1)[S. M. Barr and I. Dorsner, Phys. Rev. D 72, 015011 (2005); S. M. Barr and A. Khan, Phys. Rev. D 74, 085023 (2006)] is clearly presented. The assigned extra U(1) gauge charges give a strong constraint to build Lagrangians. The Z{sup '} discovery limits are estimated and predicted at the Tevatron and the LHC. The new contributions of the muon anomalous magnetic moment are investigated at one and two loops, and we predict that the deviation from the standard model may be explained. The electron electric dipole moment could also be generated because of the explicit CP-violation effect in the Higgs sector, and a sizable contribution is expected for a moderately sized CP phase [argument of the CP-odd Higgs], 0.1{<=}sin{delta}{<=}1[6 deg. {<=}arg(A){<=}90 deg.].

  4. 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.

  5. Magnetic excitations in a bond-centered stripe phase: spin waves far from the semiclassical limit.

    PubMed

    Vojta, Matthias; Ulbricht, Tobias

    2004-09-17

    Using a spin-only model, we compute spin excitation spectra in a bond-centered stripe state with long-range magnetic order. We employ a bond operator formalism, which naturally captures both dimerization and broken spin symmetry in a unified framework. At low energies, the spin excitations resemble spin waves, but at higher energies they are very similar to spin-one excitations of isolated spin ladders. Our theory does well describe neutron scattering data [Nature (London) 429, 534 (2004)

  6. Pulsed CO2 laser pumped by an all solid-state magnetic exciter

    NASA Astrophysics Data System (ADS)

    Shimada, T.; Noda, K.; Obara, M.; Midorikawa, K.

    1985-11-01

    An all solid-state exciter, which consists of a Silicon Controlled Rectifier (SCR) switched pulse transformer and a three stage magnetic pulse compressor, has been successfully used for pulsed CO2 laser excitation. Using the exciter, output laser energy of 240 mJ has been obtained at 1 pps under sealed-off conditions. Since this laser has no discharge switch, long lifetime operation with high repetition rate (HRR) is anticipated.

  7. Effects of citalopram on the excitability of the human motor cortex: a paired magnetic stimulation study.

    PubMed

    Robol, Elisa; Fiaschi, Antonio; Manganotti, Paolo

    2004-06-15

    Several recent reports suggest the possibility of monitoring pharmacological effects on brain excitability through transcranial magnetic stimulation (TMS). Different drugs have been studied using paired magnetic stimulation in normal subjects and patients. In particular, it has been suggested that antidepressant drugs may have an appreciable effect on motor excitability. The aim of the present study was to investigate motor area excitability in normal subjects after oral administration of a single dose of citalopram, a selective serotonin reuptake inhibitor (SSRI) antidepressant. Motor cortex excitability was studied by single and paired transcranial magnetic stimulation before and 2.5 and 36 (t1/2=36 h) h after oral administration of 30 mg of citalopram. Cortical excitability was measured using different transcranial magnetic stimulation parameters: motor threshold (MT), motor-evoked potential (MEP) amplitude and latency, motor recruitment, duration of cortical silent period (CSP), intracortical inhibition and intracortical facilitation. Spinal excitability and peripheral nerve conduction were measured by F response and M wave. Temporary but significant increases in motor threshold, motor-evoked potentials, silent period and intracortical inhibition were observed 2.5 h after drug administration, without any significant changes in motor-evoked potential amplitude and latency and spinal excitability parameters. Our findings suggest that a single oral dose of citalopram can induce significant but transitory suppression of motor cortex excitability in normal subjects.

  8. Constraint on the magnetic dipole moment of neutrinos by the tip-RGB luminosity in ω-Centauri

    NASA Astrophysics Data System (ADS)

    Arceo-Díaz, S.; Schröder, K.-P.; Zuber, K.; Jack, D.

    2015-10-01

    In this work, we use models constructed with the Eggleton code for stellar evolution, along with the photometric data of the super-rich globular cluster ω-Centauri (Sollima et al., 2004), to put a constraint on the magnetic dipole moment of neutrinos. We begin with a review of the idea proposed by Raffelt and Dearborn (1988), in which, as a consequence of a non-zero magnetic dipole moment, the tip-RGB luminosity of low mass stars gets increased over its standard value. First, we measure the dependence of the He-core mass and bolometric luminosity, at the tip-RGB, on the existing fits to characterize plasmon decay into neutrinos, namely those from Itoh et al. (1992), Haft et al. (1994), and the more recent results from Kantor and Gushakov (2007). Then, stating our definition of the tip-RGB, we revise multiple theoretical aspects: the consequences of non-standard neutrino emission on the internal structure of stellar models, its impact on the calibration of the Reimers mass-loss rate and later evolutionary phases and the influence of initial Helium abundance, metallicity, convection theory and opacities. Finally, we consider the specific case of ω-Cen. Using our tip-RGB models, and the bolometric correction obtained by the PHOENIX code for stellar atmospheres, to estimate the luminosity for canonical and non-standard evolution, also measuring the impact of the reported chemical spread in ω-Cen on our results. We find that the upper limit μν ≤ 2.2 ×10-12μB is already well constrained by observations. This result compares with the one obtained by Viaux et al. (2013), μν ≤ 2.6 ×10-12μB , from photometric study of the globular cluster M5.

  9. Magnetic dipole moments of {sup 58}Cu and {sup 59}Cu by in-source laser spectroscopy

    SciTech Connect

    Stone, N. J.; Koester, U.; Stone, J. Rikovska; Fedorov, D. V.; Fedoseyev, V. N.; Flanagan, K. T.; Hass, M.; Lakshmi, S.

    2008-06-15

    Online measurements of the magnetic dipole moments and isotope shifts of {sup 58}Cu and {sup 59}Cu by the in-source laser spectroscopy method are reported. The results for the magnetic moments are {mu} ({sup 58}Cu) =+0.52(8) {mu}{sub N},{mu}({sup 59}Cu) =+1.84(3) {mu}{sub N} and for the isotope shifts {delta}{nu}{sup 59,65}=1.72(22) GHz and {delta}{nu}{sup 58,65}=1.99(30) GHz in the transition from the 3d{sup 10}4s {sup 2}S{sub 1/2} ground state to the 3d{sup 10}4p {sup 2}P{sub 1/2} state in Cu I. The magnetic moment of {sup 58}Cu is discussed in the context of the strength of the subshell closure at {sup 56}Ni, additivity rules and large-scale shell model calculations.

  10. Alternate design concept for the SSC dipole magnet cryogenic support post

    SciTech Connect

    Lipski, A.; Nicol, T.H.; Richardson, R.

    1991-03-01

    New materials and developments in the field of advanced composites have created the opportunity to take a fresh look into the design of the cryogenic supports for SSC collider dipole cryostats. Although the present reentrant post design meets the structural and thermal requirements, its assembly requires precision and proficiency. The objective of the proposed alternate concept is to reduce the overall cost of the support post by means of simplifying and optimizing its component design and assembly process. The present shrink fitted tube assembly may potentially be replaced by injection molded parts. New resin systems with lower thermal conductivity and high strength properties enable the utilization of automated production techniques such as injection molding and filament winding. This paper will provide analysis and design information for the alternate support post concept and compare its test performance and cost to the present support post. 3 refs., 12 figs., 4 tabs.

  11. Laboratory Dipole Plasma Physics

    NASA Astrophysics Data System (ADS)

    Kesner, Jay

    2011-10-01

    Modern laboratory studies of plasma confined by a strong dipole magnet originated twenty years ago when it was learned that planetary magnetospheres have centrally-peaked plasma pressure profiles that form naturally when solar wind drives plasma circulation and heating. Unlike other internal rings devices, like spherators and octupoles, the magnetic flux tubes of the dipole field expand rapidly with radius. Unlike plasma confinement devices that obtain stability from magnetic shear and average good curvature, like tokamaks and levitrons, the dipole-confined plasma obtains stability from plasma compressibility. These two geometric characteristics of the dipole field have profound consequences: (i) plasma can be stable with local beta exceeding unity, (ii) fluctuations can drive either heat or particles inward to create stationary profiles that are strongly peaked, and (iii) the confinement of particles and energy can decouple. During the past decade, several laboratory dipole experiments and modeling efforts have lead to new understanding of interchange, centrifugal and entropy modes, nonlinear gyrokinetics, and plasma transport. Two devices, the LDX experiment at MIT and RT-1 at the University of Tokyo, operate with levitated superconducting dipole magnets. With a levitated dipole, not only is very high-beta plasma confined in steady state but, also, levitation produces high-temperature at low input power and demonstrates that toroidal magnetic confinement of plasma does not require a toroidal field. Modeling has explained many of the processes operative in these experiments, including the observation of a strong inward particle pinch. Turbulent low-frequency fluctuations in dipole confined plasma cause adiabatic transport and form a fundamental linkage between the radial variation of flux-tube volume and the centrally peaked density and pressure profiles. In collaboration with M.E. Mauel and D.T. Garnier; supported by DoE FG02-98ER54458.

  12. Density functional theory calculations on rhodamine B and pinacyanol chloride. Optimized ground state, dipole moment, vertical ionization potential, adiabatic electron affinity and lowest excited triplet state.

    PubMed

    Delgado, Juan C; Selsby, Ronald G

    2013-01-01

    The ground state configuration of the gas phase cationic dyes pinacyanol chloride and rhodamine B are optimized with HF/6-311 + G(2d,2p) method and basis set. B3PW91/6-311 + G(2df,2p) functional and basis set is used to calculate the Mulliken atom charge distribution, total molecular energy, the dipole moment, the vertical ionization potential, the adiabatic electron affinity and the lowest excited triplet state, the last three as an energy difference between separately calculated open shell and ground states. The triplet and extra electron states are optimized to find the relaxation energy. In the ground state optimization of both dyes the chloride anion migrates to a position near the center of the chromophore. For rhodamine B the benzoidal group turns perpendicular to the chromophore plane. For both dyes, the LUMO is mostly of π character associated with the aromatic part of the molecule containing the chromophore. The highest occupied MOs consist of three almost degenerate eigenvectors involving the chloride anion coordinated with σ electrons in the molecular framework. The fourth highest MO is of π character. For both molecules in the gas phase ionization process the chloride anion loses the significant fraction of electric charge. In electron capture, the excess charge goes mainly on the dye cation.

  13. Hybrid fluid-particle simulation of whistler-mode waves in a compressed dipole magnetic field: Implications for dayside high-latitude chorus

    NASA Astrophysics Data System (ADS)

    Silva, C. L.; Wu, S.; Denton, R. E.; Hudson, M. K.; Millan, R. M.

    2017-01-01

    In this work we present a methodology for simulating whistler-mode waves self-consistently generated by electron temperature anisotropy in the inner magnetosphere. We present simulation results using a hybrid fluid/particle-in-cell code that treats the hot, anisotropic (i.e., ring current) electron population as particles and the background (i.e., the cold and inertialess) electrons as fluid. Since the hot electrons are only a small fraction of the total population, warm (and isotropic) particle electrons are added to the simulation to increase the fraction of particles with mass, providing a more accurate characterization of the wave dispersion relation. Ions are treated as a fixed background of positive charge density. The plasma transport equations are coupled to Maxwell's equations and solved in a meridional plane (a 2-D simulation with 3-D fields). We use a curvilinear coordinate system that follows the topological curvature of Earth's geomagnetic field lines, based on an analytic expression for a compressed dipole magnetic field. Hence, we are able to simulate whistler wave generation at dawn (pure dipole field lines) and dayside (compressed dipole) by simply adjusting one scalar quantity. We demonstrate how, on the dayside, whistler-mode waves can be locally generated at a range of high latitudes, within pockets of minimum magnetic field, and propagate equatorward. The obtained dayside waves (in a compressed dipole field) have similar amplitude and frequency content to their dawn sector counterparts (in a pure dipole field) but tend to propagate more field aligned.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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 7Li-NMR spectroscopy measurements with an externally applied magnetic field B 0  =  9 T. We find that the magnetic dipole field component (B\\parallel\\text{dip} ) 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 θ =+{{52.5}\\circ} , while the B\\parallel\\text{dip} maximum is at θ =+{{142.5}\\circ} when B 0 is applied perpendicular to b ({{B}0}\\bot b ), where θ ={{0}\\circ} represents the direction of {{B}0}\\parallel c . Further estimation indicates that B\\parallel\\text{dip} 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 B\\parallel\\text{dip} 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.

  15. Electron beam focusing in a racetrack microtron by means of rotated two-sector dipole magnets

    NASA Astrophysics Data System (ADS)

    Delhez, J. L.; Webers, G. A.; Botman, J. I. M.; Hagedoorn, H. L.; Muzio, D.; Timmermans, C. J.

    1992-05-01

    We present an unconventional method of electron beam focusing in a racetrack microtron (RTM). The RTM bending magnets have a two-sector shape (valley and hill) and are slightly rotated in their median plane in order to guarantee closed orbits. Then, isochronism is automatically fulfilled. Comparison between this new arrangement and a previous three-sector design, inspired by Froelich [1], shows that the focusing properties are greatly improved, e.g. regarding beam acceptance and construction sensitivity. We will give a detailed description of the two-sector layout, make a comparison with the three-sector magnet (acceptance and sensitivity) and give magnet parameters for optimum performance.

  16. Magnetic flux transport and the sun's dipole moment - New twists to the Babcock-Leighton model

    NASA Technical Reports Server (NTRS)

    Wang, Y.-M.; Sheeley, N. R., Jr.

    1991-01-01

    The mechanisms that give rise to the sun's large-scale poloidal magnetic field are explored in the framework of the Babcock-Leighton (BL) model. It is shown that there are in general two quite distinct contributions to the generation of the 'alpha effect': the first is associated with the axial tilts of the bipolar magnetic regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the magnetic flux is dispersed over the surface. The general relationship between flux transport and the BL dynamo is discussed.

  17. Pygmy dipole resonance and dipole polarizability in 90Zr

    NASA Astrophysics Data System (ADS)

    Iwamoto, C.; Tamii, A.; Utsunomiya, H.; Akimune, H.; Nakada, H.; Shima, T.; Hashimoto, T.; Yamagata, T.; Kawabata, T.; Fujita, Y.; Matsubara, H.; Suzuki, T.; Fujita, H.; Shimbara, Y.; Nagashima, M.; Sakuda, M.; Mori, T.; Izumi, T.; Okamoto, A.; Kondo, T.; Lui, T.-W.; Bilgier, B.; Kozer, H. C.; Hatanaka, K.

    2014-05-01

    Electric dipole (E1) reduced transition probability B(E1) of 90Zr was obtained by the inelastic proton scattering near 0 degrees using a 295 MeV proton beam and multipole decomposition analysis of the angular distribution by the distorted-wave Born approximation with the Hartree-Fock plus random-phase approximation model and inclusion of El Coulomb excitation, and the E1 strength of the pygmy dipole resonance was found in the vicinity of the neutron threshold in the low-energy tail of the giant dipole resonance. Using the data, we plan to determine the precise dipole polarizability αD which is defined as an inversely energy-weighted sum value of the elecrric dipole strength. The dipole polarizability is expected to constrain the symmetry energy term of the neutron matter equation of state. Thus systematical measurement of the dipole polarizability is important.

  18. Spin excitations of CoCO 3 in a longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Loktev, V. M.

    1981-01-01

    The magnetization and the spectrum of spin excitations of CoCO 3 in an external magnetic field parallel to a third-order crystal axis are calculated using the model of an easy plane antiferrodielectric with spin 3/2. It is shown that with increasing field the spin projection on its quantization axis contracts due to the large single-ion anisotropy of cobalt carbonate. The dependence on the external field of the crystal absorption frequencies with excitation of spin waves and low-frequency excitations is analyzed.

  19. Determination of ground and excited state dipole moments of 4,5'-diamino[1,1':3',1''-terphenyl]-4',6'-dicarbonitrile using solvatochromic method and quantum-chemical calculations.

    PubMed

    Józefowicz, Marek; Milart, Piotr; Heldt, Janina R

    2009-11-01

    Electronic absorption and fluorescence spectra of 4,5'-diamino[1,1':3',1''-terphenyl]-4',6'-dicarbonitrile (1) were recorded at room temperature in several solvents of different polarity. The results of spectroscopic measurements are analyzed using the theory of solvatochromism, based on a dielectric continuum description of the solvent and the classical Onsager cavity model. The difference in the excited and ground state dipole moments (mu(e)-mu(g)) of the molecule under study was estimated using methods applied by Bayliss, Ooshika, McRae, Lippert, Mataga, Bakhshiev and Kawski. Finally, the influence of polarizability on the determined change of the dipole moment was discussed. Austin model 1 (AM1) semiempirical molecular calculations were carried out to estimate the ground state dipole moment.

  20. Determination of ground and excited state dipole moments of 4,5'-diamino[1,1':3',1″-terphenyl]-4',6'-dicarbonitrile using solvatochromic method and quantum-chemical calculations

    NASA Astrophysics Data System (ADS)

    Józefowicz, Marek; Milart, Piotr; Heldt, Janina R.

    2009-11-01

    Electronic absorption and fluorescence spectra of 4,5'-diamino[1,1':3',1″-terphenyl]-4',6'-dicarbonitrile ( 1) were recorded at room temperature in several solvents of different polarity. The results of spectroscopic measurements are analyzed using the theory of solvatochromism, based on a dielectric continuum description of the solvent and the classical Onsager cavity model. The difference in the excited and ground state dipole moments ( μe- μg) of the molecule under study was estimated using methods applied by Bayliss, Ooshika, McRae, Lippert, Mataga, Bakhshiev and Kawski. Finally, the influence of polarizability on the determined change of the dipole moment was discussed. Austin model 1 (AM1) semiempirical molecular calculations were carried out to estimate the ground state dipole moment.

  1. Determination of Local Magnetic Dipole Moment of the Plasma at the PUPR Cusp-Mirror Machine

    SciTech Connect

    Leal-Quiros, Edbertho; Prelas, Mark

    2006-12-04

    A novel diagnostic that allows measurement of the magnetic moment {mu} has been designed. The {mu}-Analyzer consists of a Directional Energy Analyzer and a Magnetic Hall Probe in the same detector miniature case. The Directional Energy Analyzer measures the ion temperature in the perpendicular direction to the magnetic field. On the other side, the Hall Probe measures the magnetic field. The {mu}-Analyzer is a miniature analyzer to avoid plasma perturbation. This allows the measurement of the ion temperature and the local magnetic field at the same point at the same time, therefore {mu}, the first adiabatic invariant is found. From the above parameters, the local Larmor radius also will be calculated. From the analysis of the data simultaneously in time and space, the {mu} of the Local Plasma has been determined. This result is a very important quantity, among other properties that permit one to know the stability of the magnetic confinement device using the MHD Stability Criterium, and also very important in Space Plasma Research. In addition to the above, a direct measurement of the Larmor radius of each position is also possible. The experiments have been made in a Cusp/Mirror Plasma Machine where plasma parameters such as Density and Temperature are relatively easy to change in a very wide range.

  2. Itinerant Magnetic Excitations in Antiferromagnetic CaFe2As2

    SciTech Connect

    Diallo, S.; Antropov, V.; Perring, T.; Broholm, C.; Pulikkotil, J.; Ni, N.; Bud'ko, S.; Canfield, P.; Kreyssig, A.; Goldman, A.; McQueeney, R.

    2009-05-07

    Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe{sub 2}As{sub 2} reveal steeply dispersive and well-defined spin waves up to an energy of {approx}100 meV. Magnetic excitations above 100 meV and up to the maximum energy of 200 meV are however broader in energy and momentum than the experimental resolution. While the low energy modes can be fit to a Heisenberg model, the total spectrum cannot be described as arising from excitations of a local moment system. Ab initio calculations of the dynamic magnetic susceptibility suggest that the high energy behavior is dominated by the damping of spin waves by particle-hole excitations.

  3. Developmentof the 15 T Nb3Sn dipole HD2

    SciTech Connect

    Caspi, S.; Cheng, D.W.; Dietderich, D.R.; Hafalia, A.R.; Hannaford, C.R.; Higley, H.; Lietzke, A.F.; Lizarazo, J.; McInturff, A.D.; Sabbi, G.; Ferracin, P.

    2008-06-01

    The Superconducting Magnet Program at Lawrence Berkeley National Laboratory (LBNL) is continuing the development of HD2, a 1 m long Nb{sub 3}Sn dipole generating a dipole field of 15 T in a 36 mm clear bore. With tilted (flared) ends to avoid obstructing the beam path, HD2 represents a step towards the development of cost effective accelerator quality magnets. The design has been optimized to minimize geometric harmonics and to address iron saturation and conductor magnetization effects. The support structure is based on an external aluminum shell, pre-tensioned with pressurized bladders and interference keys. Aluminum axial rods and stainless steel end plates provide longitudinal support to the coil ends during magnet excitation. This paper reports on field quality optimization and magnet parameters. The design and fabrication of the coil and structure components, and results from coil winding, reaction, and potting are also presented.

  4. Stable oscillation in spin torque oscillator excited by a small in-plane magnetic field

    SciTech Connect

    Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Ito, Takahiro; Utsumi, Yasuhiro

    2015-08-07

    Theoretical conditions to excite self-oscillation in a spin torque oscillator consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer are investigated by analytically solving the Landau-Lifshitz-Gilbert equation. The analytical relation between the current and oscillation frequency is derived. It is found that a large amplitude oscillation can be excited by applying a small field pointing to the direction anti-parallel to the magnetization of the pinned layer. The validity of the analytical results is confirmed by comparing with numerical simulation, showing good agreement especially in a low current region.

  5. Direct observation of dynamic modes excited in a magnetic insulator by pure spin current

    PubMed Central

    Demidov, V. E.; Evelt, M.; Bessonov, V.; Demokritov, S. O.; Prieto, J. L.; Muñoz, M.; Ben Youssef, J.; Naletov, V. V.; de Loubens, G.; Klein, O.; Collet, M.; Bortolotti, P.; Cros, V.; Anane, A.

    2016-01-01

    Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators. PMID:27608533

  6. 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.

  7. Hedgehog excitations in double-exchange magnetism: Energetics and electronic structure

    NASA Astrophysics Data System (ADS)

    Pekker, David; Goldbart, Paul; Salamon, Myron; Abanov, Alexander

    2004-03-01

    Topological hedgehog excitations of the magnetic state are believed to play an important role in the three-dimensional ferromagnet-to-paramagnet phase transition. This is true not only in Heisenberg magnets but also in double-exchange magnets, for which the transition is accompanied by a metal-insulator transition. The energetics and electronic structure of hedgehog excitations in double-exchange systems are investigated using a model in which the electrons move through a lattice of classical spins, to which they are coupled via Hund's Rule interactions. The core energy of hedgehog excitations is determined, as is the extent to which charge is expelled from the hedgehog cores. In settings involving pairs of hedgehogs, the manner in which the electronic energetics determines the magnetic structure is explored variationally, especially in the region between the hedgehogs.

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

    SciTech Connect

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

    2014-07-14

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

  9. Preferential Excitation of Stellar Oscillations of a Magnetar with a Tangled Magnetic Field

    NASA Astrophysics Data System (ADS)

    Bretz, Joseph; van Eysden, Anthony; Link, Bennett

    2017-01-01

    Magnetars are strongly magnetized ( 1015 Gauss) neutron stars. Some of them produce giant flares that exhibit quasi-periodic oscillations which have been attributed to stellar oscillations that modulate the emission. A tangled magnetic field model introduces a spectrum of magnetic normal modes that can explain the observed quasi-periodic oscillations, as expected from stability considerations. We show that reasonable initial conditions preferentially excite stellar oscillations, and find promising agreement with data. Funding support from Montana Space Grant Apprenticeship Program

  10. Analogue of the quantum Hall effect for neutral particles with magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Ribeiro, L. R.; Passos, E.; Furtado, C.; Sergeenkov, S.

    2017-03-01

    In this paper we investigate a possibility for the existence of an analog of the Quantum Hall Effect for neutral particles with a permanent magnetic moment μ in the presence of crossed inhomogeneous magnetic and electric fields. We predict the appearance of Hall conductivity σH = (e2 / h) ν (μ) with the Landau filling factor ν (μ) ∝μ2. The estimates of the model parameters suggest quite an optimistic possibility to experimentally verify this prediction in optically trapped clouds of atomic BEC.

  11. Effect of the. delta. (1236) resonance on magnetic dipole properties of nuclei

    SciTech Connect

    Lawson, R.D.

    1983-01-01

    The effect of the ..delta..(1236) resonance on magnetic moments, M1 transition rates and beta decay is discussed. The main effect of including this resonance is to renormalize the g-factor of the valence nucleons and explicit values for this renormalization are given. The effect on l-forbidden M1 transitions is investigated.

  12. Symmetry Analysis of Spin-Dependent Electric Dipole and Its Application to Magnetoelectric Effects

    NASA Astrophysics Data System (ADS)

    Matsumoto, Masashige; Chimata, Kosuke; Koga, Mikito

    2017-03-01

    Spin-dependent electric dipole operators are investigated group-theoretically for the emergence of an electric dipole induced by a single spin or by two spins, where the spin dependences are completely classified up to the quadratic order. For a single spin, a product of spin operators behaves as an even-parity electric quadrupole operator, which differs from an odd-parity electric dipole. The lack of the inversion symmetry allows the even- and odd-parity mixing, which leads to the electric dipole described by the electric quadruple operators. Point-group tables are given for classification of the possible spin-dependent electric dipoles and for the qualitative analysis of multiferroic properties, such as an emergent electric dipole moment coexisting with a magnetic moment, electromagnon excitation, and directional dichroism. The results can be applied to a magnetic ion in crystals or embedded in molecules at a site without the inversion symmetry. In the presence of an inversion symmetry, the electric dipole does not appear for a single spin. This is not the case for the electric dipole induced by two spins with antisymmetric spin dependence, which is known as vector spin chirality, in the presence of the inversion center between the two spins. In the absence of the inversion center, symmetric spin-dependent electric dipoles are also relevant. The detailed analysis of various symmetries of two-spin states is applied to spin dimer systems and the related multiferroic properties.

  13. 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.

  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

    2015-10-09

    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.

  15. Magnetic performance of a variable period, fast excitation, wiggler

    SciTech Connect

    Gallardo, J.; Romano, T.; van Steenbergen, A.

    1993-11-01

    With the objective of carrying out an Inverse Free Electron Laser (IFEL) electron accelerator experiment, an iron dominated (Vanadium Permandur) fast excitation, laminated (variable period length) planar wiggler, making use of copper field reflectors, has been constructed and has been measured in several period length tapering configurations. This report presents an analysis and experimental results of this wiggler, typically of which the parameters are {gamma}(w) = 3.7 cm, B(max) = 1.8{Tau}.

  16. Analytical description of the charged particle dynamics in the field of a spherical magnetic dipole

    NASA Astrophysics Data System (ADS)

    Baev, V. K.; Bogdanovich, B. Yu.; Nesterovich, A. V.

    2015-07-01

    The equations of charged particle motion in the earth's magnetic field are analyzed. Analytical data allow us to estimate important parameters of the charge dynamics, such as the charge capture conditions, oscillation amplitude and frequency, and longitudinal drift, and also relate these parameters to the parameters of the charged particles and the height of their trajectory. The results may be used in designing space vehicles intended for investigation of the near-earth space, specifically, earth's magnetosphere, with charged particle beams.

  17. Magnetic dipole moment of the doubly-closed-shell plus one proton nucleus 49Sc.

    PubMed

    Ohtsubo, T; Stone, N J; Stone, J R; Towner, I S; Bingham, C R; Gaulard, C; Köster, U; Muto, S; Nikolov, J; Nishimura, K; Simpson, G S; Soti, G; Veskovic, M; Walters, W B; Wauters, F

    2012-07-20

    The nucleus 49Sc, having a single f(7/2) proton outside doubly magic 48Ca (Z=20, N=28), is one of the very few isotopes which makes possible testing of the fundamental theory of nuclear magnetism. The magnetic moment has been measured by online β NMR of nuclei oriented at milli-Kelvin temperatures to be (+)5.616(25)  μ(N). The result is discussed in terms of a detailed theory of the structure of the magnetic moment operator, showing excellent agreement with calculated departure from the f(7/2) Schmidt limit extreme single-particle value. The measurement completes the sequence of moments of Sc isotopes with even numbers of f(7/2) neutrons: the first such isotopic chain between two major shells for which a full set of moment measurements exists. The result further completes the isotonic sequence of ground-state moments of nuclei with an odd number of f(7/2) protons coupled to a closed subshell of f(7/2) neutrons. Comparison with a recent shell-model calculation of the latter sequence is made.

  18. A magnetospheric echo after pulsed switch-on of a ground level vertical magnetic dipole

    NASA Astrophysics Data System (ADS)

    Arykov, A. A.; Maltsev, Iu. P.

    1980-04-01

    An investigation of the field of a signal reflected by the conjugate ionosphere and returned to the source is presented. It is shown that during the day, the magnetic field of the magnetospheric echo is described by a quadrupole field which originates at the moment of the arrival of the echo to the point located specularly relative to the lower edge of the ionosphere. Two zones can be defined at night, a near and a distant zone; in both zones the field is approximately quadrupolar.

  19. Improved measurement surface for MEG using magnetic-dipole sources and a spherical-multipole expansion

    NASA Astrophysics Data System (ADS)

    Argin, F.; Ahrens, H.; Klinkenbusch, L.

    2012-09-01

    The multipole representation of Magnetoencephalography (MEG) signals is known as a useful tool for distinguishing between magnetic fields arising from the brain and external disturbances. In this contribution we extend this concept and show that a closed double-layer surface with magnetometer probes is better suited to determine the corresponding multipole amplitudes αlm than a conventional single-layer surface with gradiometers and magnetometer probes. For two different source configurations we show that the αlm rapidly converge to the exact values. This proof of concept motivates to further optimize the geometry of the double-layer surface and the sensors' positions.

  20. 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.

  1. Magnetic design of trim excitations for the advanced light source storage ring sextupole

    SciTech Connect

    Marks, S.

    1995-06-01

    The Advanced Light Source (ALS) storage ring sextupole is a unique multi-purpose magnet. It is designed to operate as a sextupole with three auxiliary trim modes: horizontal steering, vertical steering, and skew quadrupole. A perturbation theory for iron-dominated magnets developed by Klaus Halbach provides the basis for this design. The three trim excitations are produced by violating sextupole symmetry and are thus perturbations of the normal sextupole excitation. The magnet was designed such that all four modes are decoupled and can be excited independently. This paper discusses the use of Halbach`s perturbation theory to design the trim functions and to evaluate the primary asymmetry in the sextupole mode, namely, a gap in the return yoke to accommodate the vacuum chamber.

  2. Magnetic design of trim excitations for the Advanced Light Source storage ring sextupole

    SciTech Connect

    Marks, S.

    1996-07-01

    The Advanced Light Source (ALS) storage ring sextupole is a unique multi-purpose magnet. It is designed to operate as a sextupole with three auxiliary trim modes: horizontal steering, vertical steering, and skew quadrupole. A perturbation theory for iron-dominated magnets developed by Klaus Halbach provides the basis for this design. The three trim excitations are produced by violating sextupole symmetry and are thus perturbations of the normal sextupole excitation. The magnet was designed such that all four modes are decoupled and can be excited independently. This paper discusses the use of Halbach`s perturbation theory to design the trim functions and to evaluate the primary asymmetry in the sextupole mode, namely, a gap in the return yoke to accommodate the vacuum chamber.

  3. Fully Suspended, Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig With Forced Excitation

    NASA Technical Reports Server (NTRS)

    Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Montague, Gerald; Duffy, Kirsten; Mehmed, Oral; Johnson, Dexter; Jansen, Ralph

    2004-01-01

    The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig, a significant advancement in the Dynamic Spin Rig (DSR), is used to perform vibration tests of turbomachinery blades and components under rotating and nonrotating conditions in a vacuum. The rig has as its critical components three magnetic bearings: two heteropolar radial active magnetic bearings and a magnetic thrust bearing. The bearing configuration allows full vertical rotor magnetic suspension along with a feed-forward control feature, which will enable the excitation of various natural blade modes in bladed disk test articles. The theoretical, mechanical, electrical, and electronic aspects of the rig are discussed. Also presented are the forced-excitation results of a fully levitated, rotating and nonrotating, unbladed rotor and a fully levitated, rotating and nonrotating, bladed rotor in which a pair of blades was arranged 180 degrees apart from each other. These tests include the bounce mode excitation of the rotor in which the rotor was excited at the blade natural frequency of 144 Hz. The rotor natural mode frequency of 355 Hz was discerned from the plot of acceleration versus frequency. For nonrotating blades, a blade-tip excitation amplitude of approximately 100 g/A was achieved at the first-bending critical (approximately 144 Hz) and at the first-torsional and second-bending blade modes. A blade-tip displacement of 70 mils was achieved at the first-bending critical by exciting the blades at a forced-excitation phase angle of 908 relative to the vertical plane containing the blades while simultaneously rotating the shaft at 3000 rpm.

  4. Optically exciting a magnetic memory - A feasibility study

    NASA Technical Reports Server (NTRS)

    Grismore, F. L.; Rhodes, J. E.

    1969-01-01

    Rare earth iron garnets were used in experiments to determine the feasibility of optically pumping a magnetic material to effect the switching process. It was found that rare earth garnets are limited by an absorption edge, only terbium and dysprosium offer a possibility of pumping at energies below the conduction band edge.

  5. Elementary excitations in magnetically ordered systems with orbital degeneracy

    SciTech Connect

    Joshi, A.; Ma, M. ); Mila, F. ); Shi, D.N. College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing, Peoples Republic of ); Zhang, F.C. )

    1999-09-01

    The generalized Holstein-Primakoff transformation is used to develop a quantum flavor wave theory for spin systems with orbital degeneracy. Elementary excitations of ordered ground states consist of spin, orbital, and spin-orbital waves. Spin and spin-orbital waves couple to each other due to orbital anisotropy and Hund[close quote]s rule, resulting in modes observable by inelastic neutron scattering. In the SU(4) limit, flavor waves are dispersionless along one or more directions, and give rise to quantum fluctuations of reduced dimensionality. [copyright] [ital 1999] [ital The American Physical Society

  6. A magnetizing system for dichroism measurements in soft x-ray emission excited by synchrotron radiation

    SciTech Connect

    Dallera, C.; Ghiringhelli, G.; Braicovich, L.

    1996-02-01

    We present the design and performance of a magnetic circuit suitable for magnetizing solid samples in the measurements of soft x-ray emission dichroism excited by synchrotron radiation. The system allows a variety of samples to be magnetized and satisfies the rather stringent geometrical constraints due to the need for minimizing the effect of photon self-absorption by the sample. The magnetic circuit is ultrahigh vacuum compatible, can reach about 2800 G, and allows fine adjustment of sample position. {copyright} {ital 1996 American Institute of Physics.}

  7. Effect of excitation field strength on magnetic Barkhausen noise profile in case carburized EN 36 steel

    NASA Astrophysics Data System (ADS)

    Blaow, M. M.; Shaw, B. A.

    2015-03-01

    The sensitivity of magnetic Barkhausen noise (MBN) profile to changes in the excitation field strength has been investigated in case carburized EN36 steel. In general, the 0.5 mm case depth EN 36 steel specimen induces a double peak profile indicative of inhomogeneity through the detected depth in the magnetized landscape. Various excitation field amplitudes have been applied to the electromagnet to generate various excitation fields on the specimen surface. Excitation field at the lowest level induced an MBN emission of two peaks of equivalent heights at low current value. The first peak occurs at lower field than the second peak in each half magnetization cycle. As the excitation field increases, the height of both peaks increased but the second peak, at higher field, increases in a higher rate than that of the first peak at lower field. Beyond certain magnetizing voltage, both peaks heights began to saturate and no further increase in the MBN intensity has been noticed. The results are discussed on the basis of the available theories on MBN.

  8. The Rocketdyne Multifunction Tester. Part 2: Operation of a Radial Magnetic Bearing as an Excitation Source

    NASA Technical Reports Server (NTRS)

    Hawkins, L. A.; Murphy, Brian T.; Lang, K. W.

    1991-01-01

    The operation of the magnetic bearing used as an excitation source in the Rocketdyne Multifunction Tester is described. The tester is scheduled for operation during the summer of 1990. The magnetic bearing can be used in two control modes: (1) open loop mode, in which the magnetic bearing operates as a force actuator; and (2) closed loop mode, in which the magnetic bearing provides shaft support. Either control mode can be used to excite the shaft; however, response of the shaft in the two control modes is different due to the alteration of the eigenvalues by closed loop mode operation. A rotordynamic model is developed to predict the frequency response of the tester due to excitation in either control mode. Closed loop mode excitation is shown to be similar to the excitation produced by a rotating eccentricity in a conventional bearing. Predicted frequency response of the tester in the two control modes is compared, and the maximum response is shown to be the same for the two control modes when synchronous unbalance loading is not considered. The analysis shows that the response of this tester is adequate for the extraction of rotordynamic stiffness, damping, and inertia coefficients over a wide range of test article stiffnesses.

  9. Magnetic Excitation Spectrum of FeTe1-xSex

    NASA Astrophysics Data System (ADS)

    Lumsden, M. D.; Christianson, A. D.; Goremychkin, E. A.; Nagler, S. E.; Mook, H. A.; Stone, M. B.; Abernathy, D. L.; Guidi, T.; MacDougall, G. J.; de La Cruz, C.; Sefat, A. S.; McGuire, M. A.; Sales, B. C.; Mandrus, D.

    2010-03-01

    The magnetic excitation spectrum of single crystal samples of the bulk superconductor FeTe0.51Se0.49 and Fe1.04Te0.73Se0.27 (not a bulk superconductor) have been studied using inelastic neutron scattering. Both samples exhibit incommensurate magnetic excitations despite the lack of long-range magnetic order. These incommensurate excitations are very two-dimensional in nature and persist to energies greater than 250 meV. The incommensurate excitations originate from a 2d wavevector near (1/2, 1/2), where the resonance was observed for the bulk superconductor FeTe0.51Se0.49, and broaden with increasing energy transfer. The spectrum exhibits four-fold symmetry about the (1,0) wavevector (the square lattice (π, π) point) consistent with the symmetry of the underlying Fe square lattice. The excitations can be characterized by the same model and the incommensuration is parameterized by the same wavevector as the high-TC cuprates demonstrating commonality in the magnetism of these two classes of unconventional superconductors.

  10. High power repetitive excimer lasers pumped by an all solid state magnetic exciter

    NASA Astrophysics Data System (ADS)

    Kobayashi, Osamu; Noda, Koji; Shimada, Tsutomu; Obara, Minoru

    1986-01-01

    In a high repetition rate excimer laser operation, the lifetime of the exciter is one of the most important problems. To attain a nearly endless lifetime of the excimer laser exciter, an all-solid-state exciter has been developed which consists of a high-voltage transformer switched by a silicon-controlled rectifier, producing a pulse whose energy and duration are 11.2 J and 8 microns, respectively, and a three-stage magnetic compressor. With a 1.4-ohm dummy load, output peak power, energy/pulse, and pulse duration were 100 MW, 5.2 J, and 100 ns, respectively. The electrical efficiency of the exciter was 47 percent. The energy loss of 6 J in the exciter was due both to the core loss and the transfer loss. It should be noted that the time jitter between the SCR gate input pulse and the output voltage pulse was less than 12 ns.

  11. Neutron Scattering Study of Low Energy Magnetic Excitation in FeTeSe System

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Schneeloch, John; Matsuda, Masaaki; Christianson, A. D.; Gu, Genda; Zaliznyak, I. A.; Xu, Guangyong; Tranquada, J. M.; Birgeneau, R. J.

    2014-03-01

    We have performed neutron scattering and magnetization/transport measurements on a series of FeTe1-xSex system single crystals to study the interplay between magnetism and superconductivity. Comparing to pure FeTe1-xSex compounds, extra Fe and Ni/Cu doping on Fe-site can change physics properties of these samples, including resistivity, magnetization and superconducting properties. Our neutron scattering studies also show the Fe-site doping change low energy magnetic spectrum, including the magnetic excitations intensity, position and magnetic correlation length in these samples. On the other hand, the temperature dependence of the low energy magnetic fluctuations are also found to be different depending on the composition. This work is supported by the Office of Basic Energy Sciences, DOE.

  12. Influence of Temperature and Magnetic Field on the First Excited State of a Quantum Pseudodot

    NASA Astrophysics Data System (ADS)

    Cai, Chun-Yu; Zhao, Cui-Lan; Xiao, Jing-Lin

    2017-02-01

    Investigations on the properties of excited states of complex quantum systems can not only reveal the internal structure and properties of the system but also verify the accuracy of quantum theory. In the case of strong electron-longitudinal optical phonon coupling in a quantum pseudodot with an external magnetic field, the first excited state and transition frequency can be obtained by using the Pekar variational method and quantum statistics theory. Numerical calculations for CsI crystal show that (1) they are increasing functions of the magnetic field, and (2) they will first decrease and then increase as the temperature is increased from a low value.

  13. Spin polarization effects on magnetic dipole moment of 153,155Eu

    NASA Astrophysics Data System (ADS)

    Hoşgör, Gamze; Yakut, Hakan; Tabar, Emre

    2017-02-01

    Using the Quasiparticle Phonon Nuclear Model (QPNM) and taking into account the spin-spin interaction the effects of the spin polarization on the intrinsic magnetic moments (gK) of 153-155Eu isotopes have been studied. Our calculations indicated that because of the spin polarization, the spin gyromagnetic factors (gs) of the nucleons in the nucleus reduce noticeable from its free nucleon value and the spin-spin interactions play an important role in the renormalization (gse f f .) of the gs factors. A very good reproduction of the phenomenological quenching of gs factor from its free values (gse f f≅0.6 -0.7 gsf r e e) is obtained. The calculated values of effective gse f f and gK are also in fair agreementwith the experiment data.

  14. Measurement of the electronic transition dipole moment by Autler-Townes splitting: Comparison of three- and four-level excitation schemes for the Na2 A 1Σu+-X 1Σg+ system

    NASA Astrophysics Data System (ADS)

    Ahmed, E.; Hansson, A.; Qi, P.; Kirova, T.; Lazoudis, A.; Kotochigova, S.; Lyyra, A. M.; Li, L.; Qi, J.; Magnier, S.

    2006-02-01

    We present a fundamentally new approach for measuring the transition dipole moment of molecular transitions, which combines the benefits of quantum interference effects, such as the Autler-Townes splitting, with the familiar R-centroid approximation. This method is superior to other experimental methods for determining the absolute value of the R-dependent electronic transition dipole moment function μe(R), since it requires only an accurate measurement of the coupling laser electric field amplitude and the determination of the Rabi frequency from an Autler-Townes split fluorescence spectral line. We illustrate this method by measuring the transition dipole moment matrix element for the Na2AΣu+1(v'=25,J'=20e)-XΣg+1(v″=38,J″=21e) rovibronic transition and compare our experimental results with our ab initio calculations. We have compared the three-level (cascade) and four-level (extended Λ) excitation schemes and found that the latter is preferable in this case for two reasons. First, this excitation scheme takes advantage of the fact that the coupling field lower level is outside the thermal population range. As a result vibrational levels with larger wave function amplitudes at the outer turning point of vibration lead to larger transition dipole moment matrix elements and Rabi frequencies than those accessible from the equilibrium internuclear distance of the thermal population distribution. Second, the coupling laser can be "tuned" to different rovibronic transitions in order to determine the internuclear distance dependence of the electronic transition dipole moment function in the region of the R-centroid of each coupling laser transition. Thus the internuclear distance dependence of the transition moment function μe(R) can be determined at several very different values of the R centroid. The measured transition dipole moment matrix element for the Na2AΣu+1(v'=25,J'=20e)-XΣg+1(v″=38,J″=21e) transition is 5.5±0.2D compared to our ab initio value

  15. Measurement of the electronic transition dipole moment by Autler-Townes splitting: Comparison of three- and four-level excitation schemes for the Na2 A 1Sigma(u)+ - X 1Sigma(g)+ system.

    PubMed

    Ahmed, E; Hansson, A; Qi, P; Kirova, T; Lazoudis, A; Kotochigova, S; Lyyra, A M; Li, L; Qi, J; Magnier, S

    2006-02-28

    We present a fundamentally new approach for measuring the transition dipole moment of molecular transitions, which combines the benefits of quantum interference effects, such as the Autler-Townes splitting, with the familiar R-centroid approximation. This method is superior to other experimental methods for determining the absolute value of the R-dependent electronic transition dipole moment function mu(e)(R), since it requires only an accurate measurement of the coupling laser electric field amplitude and the determination of the Rabi frequency from an Autler-Townes split fluorescence spectral line. We illustrate this method by measuring the transition dipole moment matrix element for the Na2 A 1Sigma(u)+ (v' = 25, J' = 20e)-X 1Sigma(g)+ (v" = 38, J" = 21e) rovibronic transition and compare our experimental results with our ab initio calculations. We have compared the three-level (cascade) and four-level (extended Lambda) excitation schemes and found that the latter is preferable in this case for two reasons. First, this excitation scheme takes advantage of the fact that the coupling field lower level is outside the thermal population range. As a result vibrational levels with larger wave function amplitudes at the outer turning point of vibration lead to larger transition dipole moment matrix elements and Rabi frequencies than those accessible from the equilibrium internuclear distance of the thermal population distribution. Second, the coupling laser can be "tuned" to different rovibronic transitions in order to determine the internuclear distance dependence of the electronic transition dipole moment function in the region of the R-centroid of each coupling laser transition. Thus the internuclear distance dependence of the transition moment function mu(e)(R) can be determined at several very different values of the R centroid. The measured transition dipole moment matrix element for the Na2 A 1Sigma(u)+ (v' = 25, J' = 20e)-X 1Sigma(g)+ (v" = 38, J" = 21e

  16. A Magnetic Suspension and Excitation System for Spin Vibration Testing of Turbomachinery Blades

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter; Brown, Gerald V.; Mehmed, Oral

    1998-01-01

    The Dynamic Spin Rig (DSR) is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. A heteropolar radial active magnetic bearing was integrated into the DSR to provide non-contact magnetic suspension and mechanical excitation of the rotor to induce turbomachinery blade vibrations. The magnetic bearing replaces one of the two existing conventional radial ball bearings. Prior operation of the DSR used two voice-coil type linear electromagnetic shakers which provided axial excitation of the rotor. The new magnetic suspension and excitation system has provided enhanced testing capabilities. Tests were performed at high rotational speeds for longer duration and higher vibration amplitudes. Some characteristics of the system include magnetic bearing stiffness values up to 60,000 lb./in., closed loop control bandwidth around 500 Hz, and multi-directional radial excitation of the rotor. This paper reports on the implementation and operation of this system and presents some test results using this system.

  17. Pulsed currents carried by whistlers. I - Excitation by magnetic antennas

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Time-varying plasma currents associated with low-frequency whistlers have been investigated experimentally. Pulsed currents are induced in the uniform, boundary-free interior of a large laboratory plasma by means of insulated magnetic antennas. The time-varying magnetic field is measured in three dimensions, and the current density is calculated from del x B(r,t) = mu(0)J, where J includes the displacement current density. Typical fields B(r,t) and J(r,t) induced by a magnetic loop antenna show three-dimensional helices due to linked toroidal and solenoidal field topologies. Constant amplitude and phase surfaces assume conical shapes since the propagation speed along B0 is higher than oblique to B0. The electric field in the wave packet contains both inductive and space-charge contributions, the latter arising from the different dynamics of electrons and ions. The dominant electric field in a whistler packet is a radial space-charge field.

  18. Single crystal growth and magnetic excitations of transistion metal oxide CoV2 O6

    NASA Astrophysics Data System (ADS)

    Stockdale, Christopher; Wallington, F.; Taylor, J. W.; Garcia-Sakai, V.; Arevalo-Lopez, A. M.; Attfield, P.; Stock, C.

    2015-03-01

    Low-dimensional magnetic materials are an area of interest due to their unusual properties such as metamagnetism and magnetization plateaus. Solid state synthesis has produced polycrystalline CoV2O6 which exists in two polymorphs: one with a monoclinic structure, and the other with a triclinic structure. Single crystals have been grown from polycrystalline CoV2O6 using the flux method under vacuum and are large enough to aid in single crystal neutron diffraction. Magnetic excitations have been measured using powder neutron diffraction in the low temperatures regime with variable energy. The magnetic excitations have been compared between the two phases. The energy of the system has been modelled in terms of the spin-orbit coupling, structural distortions, and the crystal field and compared to neutron data.

  19. Excitation and propagation of an electromagnetic pulse in magnetized plasma in the low-hybrid frequency range

    NASA Astrophysics Data System (ADS)

    Shirokov, E. A.; Chugunov, Yu. V.

    2013-01-01

    We analyze specific features of slow quasi-static waves excited in the low-hybrid frequency band by a source whose dimensions are much smaller than electromagnetic wavelength. Main attention in this paper is given to an analysis of emission of harmonic signals by a dipole source in pulsed mode. First, the issue of influence of electromagnetic, thermal, and collision corrections in the dispersion equation on the field structure has been studied. Second, the structure of electric and magnetic fields near the resonant cone has been analyzed: in particular, effects of group delay and anomalous spreading of signals are considered. Thus constructed theory explains results of the OEDIPUS-C experiment, in which, for example, already at distances of order of ten wavelengths a signal delay of approximately 10-4 s was observed. Finally, we have studied some aspects of the inverse problem of electrodynamics: the role played in field formation by smoothness of charge distribution over antenna is demonstrated, and a class of smooth distributions of charge on antenna is found that form a preset field structure.

  20. Magnetic dipole moments near 132Sn: Measurement on isomeric {11}/{2 -} states in odd- A131Te and 133Te by NMR/ON

    NASA Astrophysics Data System (ADS)

    White, G.; Rikovska, J.; Stone, N. J.; Copnell, J.; Towner, I. S.; Oros, A. M.; Heyde, K.; Fogelberg, B.; Jacobsson, L.; Gustavsson, F.

    1998-09-01

    On-line low temperature nuclear orientation (OLNO) experiments have been performed on the odd- A Te isotopes 131Te and 133Te using the technique of nuclear magnetic resonance on oriented nuclei (NMR/ON). The magnetic moments of the isomeric {11}/{2 -} states have been measured extending the known data on these states in the Te isotopes up to the neutron shell closure at N = 82. The contribution to the {11}/{2 -} magnetic moment in 133Te due to core polarisation is calculated using an RPA shell model as well as corrections to the magnetic dipole operator caused by mesonic exchange currents. The neutron number dependence of the magnetic moments of the {11}/{2 -} isomers in heavy Te isotopes is discussed in terms of particle-core coupling model (PCM) calculations.

  1. Ordering, thermal excitations and phase transitions in dipolar coupled mono-domain magnet arrays

    NASA Astrophysics Data System (ADS)

    Kapaklis, Vassilios

    2015-03-01

    Magnetism has provided a fertile test bed for physical models, such as the Heisenberg and Ising models. Most of these investigations have focused on solid materials and relate to their atomic properties such as the atomic magnetic moments and their interactions. Recently, advances in nanotechnology have enabled the controlled patterning of nano-sized magnetic particles, which can be arranged in extended lattices. Tailoring the geometry and the magnetic material of these lattices, the magnetic interactions and magnetization reversal energy barriers can be tuned. This enables interesting interaction schemes to be examined on adjustable length and energy scales. As a result such nano-magnetic systems represent an ideal playground for the study of physical model systems, being facilitated by direct magnetic imaging techniques. One particularly interesting case is that of systems exhibiting frustration, where competing interactions cannot be simultaneously satisfied. This results in a degeneracy of the ground state and intricate thermodynamic properties. An archetypical frustrated physical system is water ice. Similar physics can be mirrored in nano-magnetic arrays, by tuning the arrangement of neighboring magnetic islands, referred to as artificial spin ice. Thermal excitations in such systems resemble magnetic monopoles. In this presentation key concepts related to nano-magnetism and artificial spin ice will be introduced and discussed, along with recent experimental and theoretical developments.

  2. Excitation of magnetization using a modulated radiation damping field.

    PubMed

    Walls, Jamie D; Huang, Susie Y; Lin, Yung-Ya

    2006-10-12

    In this work, pulsed-field gradients are used to modulate the radiation damping field generated by the detection coil in an NMR experiment in order that spins with significantly different chemical shifts can affect one another via the radiation damping field. Experiments performed on solutions of acetone/water and acetone/DMSO/water demonstrate that spins with chemical shift differences much greater than the effective radiation damping field strength can still be coupled by modulating the radiation damping field. Implications for applications in high-field NMR and for developing sensitive magnetization detectors are discussed.

  3. FAST TRACK COMMUNICATION: Magnetic excitations of Fe1 + ySexTe1 - x in magnetic and superconductive phases

    NASA Astrophysics Data System (ADS)

    Babkevich, P.; Bendele, M.; Boothroyd, A. T.; Conder, K.; Gvasaliya, S. N.; Khasanov, R.; Pomjakushina, E.; Roessli, B.

    2010-04-01

    We have used inelastic neutron scattering and muon-spin rotation to compare the low energy magnetic excitations in single crystals of superconducting Fe1.01Se0.50Te0.50 and non-superconducting Fe1.10Se0.25Te0.75. We confirm the existence of a spin resonance in the superconducting phase of Fe1.01Se0.50Te0.50, at an energy of 7 meV and a wavevector of (1/2, 1/2, 0). The non-superconducting sample exhibits two incommensurate magnetic excitations at (1/2, 1/2, 0) ± (0.18, - 0.18, 0) which rise steeply in energy, but no resonance is observed at low energies. A strongly dispersive low energy magnetic excitation is also observed in Fe1.10Se0.25Te0.75 close to the commensurate antiferromagnetic ordering wavevector (1/2 - δ, 0, 1/2), where δ≈0.03. The magnetic correlations in both samples are found to be quasi-two-dimensional in character and persist well above the magnetic (Fe1.10Se0.25Te0.75) and superconducting (Fe1.01Se0.50Te0.50) transition temperatures.

  4. Ferrofluid Photonic Dipole Contours

    NASA Astrophysics Data System (ADS)

    Snyder, Michael; Frederick, Jonathan

    2008-03-01

    Understanding magnetic fields is important to facilitate magnetic applications in diverse fields in industry, commerce, and space exploration to name a few. Large electromagnets can move heavy loads of metal. Magnetic materials attached to credit cards allow for fast, accurate business transactions. And the Earth's magnetic field gives us the colorful auroras observed near the north and south poles. Magnetic fields are not visible, and therefore often hard to understand or characterize. This investigation describes and demonstrates a novel technique for the visualization of magnetic fields. Two ferrofluid Hele-Shaw cells have been constructed to facilitate the imaging of magnetic field lines [1,2,3,4]. We deduce that magnetically induced photonic band gap arrays similar to electrostatic liquid crystal operation are responsible for the photographed images and seek to mathematically prove the images are of exact dipole nature. We also note by comparison that our photographs are very similar to solar magnetic Heliosphere photographs.

  5. Dipole-dipole interaction between rubidium Rydberg atoms

    SciTech Connect

    Altiere, Emily; Fahey, Donald P.; Noel, Michael W.; Smith, Rachel J.; Carroll, Thomas J.

    2011-11-15

    Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Foerster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that interact. Dipole-dipole interaction spectra are presented for initially excited rubidium nd states for n=31 to 46 and for four different pairs of initially excited rubidium ns states. We also present the dipole-dipole interaction spectra for individual rubidium 32d (j, m{sub j}) fine structure levels that have been selectively excited. The data are compared to calculated spectra.

  6. Magnetic Excitations in Transition-metal Oxides Studied by Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Braden, M.

    2008-03-01

    Inelastic neutron scattering using a triple axis spectrometer is a very efficient tool to analyze magnetic excitations. We will discuss several recent experiments on transition-metal oxides where orbital degrees of freedom play an important role. Different kinds of experimental techniques including longitudinal and spherical polarization analysis were used in order to determine not only magnon frequencies but also polarization vectors. In layered ruthenates bands of different orbital character contribute to the magnetic excitations which are of both, ferromagnetic and antiferromagnetic, character. The orbital dependent magnetic excitations seem to play different roles in the superconducting pairing as well as in the metamagnetism . In manganates the analysis of the magnon dispersion in the charge and orbital ordered phase yields direct insight into the microscopic coupling of orbital and magnetic degrees of freedom and helps understanding, how the switching between metallic and insulating phases in manganates may occur. In multiferroic TbMnO3 the combination of our polarized neutron scattering results with the infrared measurements identifies a soft collective excitation of hybridized magnon-phonon character.

  7. X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

    SciTech Connect

    Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; Tian, Di; Kim, J.; Upton, M. H.; Casa, D.; Gog, T.; Islam, Z.; Jeon, Byung -Gu; Kim, Kee Hoon; Desgreniers, S.; Kim, Yong Baek; Julian, S. J.; Kim, Young -June

    2016-07-06

    We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (~6 to 300 K) and pressures (~0.1 to 17 GPa) studied. We have also investigated the electronic and magnetic excitations in single-crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high-resolution Ir L-3-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ~3-5 eV, spin-orbit excitations at ~ 0.5-1 eV, and broad low-lying excitations below ~0.15 eV. In single-crystal samples of "Eu-rich" Eu2Ir2O7 (found to possess an actual stoichiometry of Eu2.18Ir1.82O7.06) we observe highly damped magnetic excitations at ~45 meV, which display significant momentum dependence. Here, we compare these results with recent dynamical structure factor calculations

  8. Magnetic vortex core reversal by excitation with short bursts of an alternating field.

    PubMed

    Van Waeyenberge, B; Puzic, A; Stoll, H; Chou, K W; Tyliszczak, T; Hertel, R; Fähnle, M; Brückl, H; Rott, K; Reiss, G; Neudecker, I; Weiss, D; Back, C H; Schütz, G

    2006-11-23

    The vortex state, characterized by a curling magnetization, is one of the equilibrium configurations of soft magnetic materials and occurs in thin ferromagnetic square and disk-shaped elements of micrometre size and below. The interplay between the magnetostatic and the exchange energy favours an in-plane, closed flux domain structure. This curling magnetization turns out of the plane at the centre of the vortex structure, in an area with a radius of about 10 nanometres--the vortex core. The vortex state has a specific excitation mode: the in-plane gyration of the vortex structure about its equilibrium position. The sense of gyration is determined by the vortex core polarization. Here we report on the controlled manipulation of the vortex core polarization by excitation with small bursts of an alternating magnetic field. The vortex motion was imaged by time-resolved scanning transmission X-ray microscopy. We demonstrate that the sense of gyration of the vortex structure can be reversed by applying short bursts of the sinusoidal excitation field with amplitude of about 1.5 mT. This reversal unambiguously indicates a switching of the out-of-plane core polarization. The observed switching mechanism, which can be understood in the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application in data storage.

  9. Electron doping evolution of the magnetic excitations in NaFe1-xCoxAs

    DOE PAGES

    Carr, Scott V.; Zhang, Chenglin; Song, Yu; ...

    2016-06-13

    We use time-of-flight (TOF) inelastic neutron scattering (INS) spectroscopy to investigate the doping dependence of magnetic excitations across the phase diagram of NaFe1-xCoxAs with x = 0, 0.0175, 0.0215, 0.05, and 0.11. The effect of electron-doping by partially substituting Fe by Co is to form resonances that couple with superconductivity, broaden and suppress low energy (E 80 meV) spin excitations compared with spin waves in undoped NaFeAs. However, high energy (E > 80 meV) spin excitations are weakly Co-doping dependent. Integration of the local spin dynamic susceptibility "(!) of NaFe1-xCoxAs reveals a total fluctuating moment of 3.6 μ2 B/Fe andmore » a small but systematic reduction with electron doping. The presence of a large spin gap in the Cooverdoped nonsuperconducting NaFe0.89Co0.11As suggests that Fermi surface nesting is responsible for low-energy spin excitations. These results parallel Ni-doping evolution of spin excitations in BaFe2-xNixAs2, confirming the notion that low-energy spin excitations coupling with itinerant electrons are important for superconductivity, while weakly doping dependent high-energy spin excitations result from localized moments.« less

  10. Magnetic Field Dependence of Excitations Near Spin-Orbital Quantum Criticality

    NASA Astrophysics Data System (ADS)

    Biffin, A.; Rüegg, Ch.; Embs, J.; Guidi, T.; Cheptiakov, D.; Loidl, A.; Tsurkan, V.; Coldea, R.

    2017-02-01

    The spinel FeSc2 S4 has been proposed to realize a near-critical spin-orbital singlet (SOS) state, where entangled spin and orbital moments fluctuate in a global singlet state on the verge of spin and orbital order. Here we report powder inelastic neutron scattering measurements that observe the full bandwidth of magnetic excitations and we find that spin-orbital triplon excitations of an SOS state can capture well key aspects of the spectrum in both zero and applied magnetic fields up to 8.5 T. The observed shift of low-energy spectral weight to higher energies upon increasing applied field is naturally explained by the entangled spin-orbital character of the magnetic states, a behavior that is in strong contrast to spin-only singlet ground state systems, where the spin gap decreases upon increasing applied field.

  11. Magnetic Excitations in the Geometric Frustrated Multiferroic CuCrO2

    SciTech Connect

    Frontzek, Matthias D; Barilo, Sergei; Christianson, Andrew D; Ehlers, Georg; Fishman, Randy Scott; Haraldsen, Jason T; Podlesnyak, Andrey A; Sefat, A. S.; Matsuda, Masaaki; Shiryaev, Sergei; Qiu, Y.; Copley, J.R.D.

    2011-01-01

    In this paper detailed neutron scattering measurements of the magnetic excitation spectrum of \\CCO\\ in the ordered state below $T_{\\rm{N1}}=24.2$~K are presented. The spectra are analyzed using a model Hamiltonian which includes intralayer-exchange up to the next-next-nearest neighbor and interlayer-exchange. We obtain a definite parameter set and show that exchange interaction terms beyond the next-nearest neighbor are important to describe the inelastic excitation spectrum. The magnetic ground state structure generated with our parameter set is in agreement with the structure proposed for \\CCO\\ from the results of single crystal diffraction experiments previously published. We argue that the role of the interlayer exchange is crucial to understand the incommensurability of the magnetic structure as well as the spin-charge coupling mechanism.

  12. Compact magnetic antennas for directional excitation of surface plasmons.

    PubMed

    Liu, Yongmin; Palomba, Stefano; Park, Yongshik; Zentgraf, Thomas; Yin, Xiaobo; Zhang, Xiang

    2012-09-12

    Plasmonics is considered as one of the most promising candidates for implementing the next generation of ultrafast and ultracompact photonic circuits. Considerable effort has been made to scale down individual plasmonic components into the nanometer regime. However, a compact plasmonic source that can efficiently generate surface plasmon polaritons (SPPs) and deliver SPPs to the region of interest is yet to be realized. Here, bridging the optical antenna theory and the recently developed concept of metamaterials, we demonstrate a subwavelength, highly efficient plasmonic source for directional generation of SPPs. The designed device consists of two nanomagnetic resonators with detuned resonant frequencies. At the operating wavelength, incident photons can be efficiently channeled into SPP waves modulated by the electric field polarization. By tailoring the relative phase at resonance and the separation between the two nanoresonators, SPPs can be steered to predominantly propagate along one specific direction. This novel magnetic nanoantenna paves a new way to manipulate photons in the near-field, and also could be useful for SPP-based nonlinear applications, active modulations, and wireless optical communications.

  13. Small Amplitude Dynamics of Nonhomogeneous Magnetization Distributions: The Excitation Spectrum of Stripe Domains

    NASA Astrophysics Data System (ADS)

    Ebels, Ursula; Buda, Liliana D.; Ounadjela, Kamel; Wigen, Phillip E.

    The general purpose of this review is to introduce to the dynamics of small amplitude excitations of nonhomogeneous magnetization distributions. This is in contrast to the dynamics of the magnetization reversal process, which corresponds to large amplitude perturbations, discussed in other contributions of this book. Small amplitude oscillations can be studied by ferromagnetic resonance or Brillouin light scattering. The latter technique isused to investigate the excitation spectrum in laterally constrained structures.This review introduces ferromagnetic resonance and focuses on the role of the pumping field orientation. Upon varying the pumping field orientation, fundamental modes can be selectively excited, giving, in particular, access to regions of varying magnetic orientation. This is demonstrated for the excitation spectrum of magnetic domains and domain walls of the stripe domain structure in metallic thin films. These stripe domains can be considered laterally constrained magnetic units 40-100 nm wide, separated by domain walls.Such experiments provide information on the domain and domain wall structure and in principle yield the internal fields and the coupling fields of the domains, as well as the wall mass and the stabilizing forces of the domain walls. The wall mass itself is a dynamic parameter which intervenes upon wall acceleration but is of less importance when considering steady-state wall propagation in the magnetization reversal process. However, the wall mass depends sensitively on the spin configuration inside the wall, and therefore resonance experiments can provide insight into the structure of the domain wall. The wall structure, on the other hand, plays an important role in spin-polarized transport experiments, investigating the contribution of a domain wall to the resistance [1] or the transfer of momentum from the conduction electrons to the wall [2,3].

  14. Preoperative localization of the central sulcus by dipole source analysis of early somatosensory evoked potentials and three-dimensional magnetic resonance imaging.

    PubMed

    Buchner, H; Adams, L; Knepper, A; Rüger, R; Laborde, G; Gilsbach, J M; Ludwig, I; Reul, J; Scherg, M

    1994-05-01

    Surgery of lesions within or close to the central area of the brain always carries the risk of iatrogenic motor or sensory deficits. Functional localization by means of intraoperative direct stimulation of the motor area or by recording somatosensory evoked potentials (SSEP's) from the surface of the somatosensory cortex is believed to reduce the operative risk. The authors introduce the combination of dipole source analysis of scalp-recorded SSEP's with three-dimensional (3-D) magnetic resonance (MR) imaging as a tool for preoperative localization of the central sulcus. This provides information on both functional and structural localization for preoperative planning. Four repeated measurements of right and left median nerve SSEP's were obtained from 20 subjects. Dipole source analysis showed a retest reliability of the 3-D localization error of 2.9 +/- 2.0 mm. Compared to the MR evaluation, dipole source analysis was found to mark the central sulcus within 3 mm for 15 conditions (subjects x side of stimulation), while the 3-D MR measurement was accurate to within 6 mm for 10 conditions and 9 mm for 14 conditions. Dipole locations were confirmed in six patients who underwent surgery of the central region. With respect to this application, dipole source analysis combined with 3-D MR imaging appears to be a valuable tool for preoperative functional localization. The accuracy in localization will be further improved when realistic head models become available that can take into account individual head geometry. Further development of the proposed new method holds promise that evoked potentials and electroencephalography will gain greater use in presurgical functional localization.

  15. Suppression of magnetic excitations near the surface of the topological Kondo insulator SmB6

    NASA Astrophysics Data System (ADS)

    Biswas, P. K.; Legner, M.; Balakrishnan, G.; Hatnean, M. Ciomaga; Lees, M. R.; Paul, D. McK.; Pomjakushina, E.; Prokscha, T.; Suter, A.; Neupert, T.; Salman, Z.

    2017-01-01

    We present a detailed investigation of the temperature and depth dependence of the magnetic properties of the three-dimensional topological Kondo insulator SmB6, in particular, near its surface. We find that local magnetic field fluctuations detected in the bulk are suppressed rapidly with decreasing depths, disappearing almost completely at the surface. We attribute the magnetic excitations to spin excitons in bulk SmB6, which produce local magnetic fields of about ˜1.8 mT fluctuating on a time scale of ˜60 ns . We find that the excitonic fluctuations are suppressed when approaching the surface on a length scale of ˜40 -90 nm , accompanied by a small enhancement in static magnetic fields. We associate this length scale to the size of the excitonic state.

  16. 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.

  17. Spontaneously Fluctuating Motor Cortex Excitability in Alternating Hemiplegia of Childhood: A Transcranial Magnetic Stimulation Study

    PubMed Central

    Stern, William M.; Desikan, Mahalekshmi; Hoad, Damon; Jaffer, Fatima; Strigaro, Gionata; Sander, Josemir W.; Rothwell, John C.; Sisodiya, Sanjay M.

    2016-01-01

    Background Alternating hemiplegia of childhood is a very rare and serious neurodevelopmental syndrome; its genetic basis has recently been established. Its characteristic features include typically-unprovoked episodes of hemiplegia and other transient or more persistent neurological abnormalities. Methods We used transcranial magnetic stimulation to assess the effect of the condition on motor cortex neurophysiology both during and between attacks of hemiplegia. Nine people with alternating hemiplegia of childhood were recruited; eight were successfully tested using transcranial magnetic stimulation to study motor cortex excitability, using single and paired pulse paradigms. For comparison, data from ten people with epilepsy but not alternating hemiplegia, and ten healthy controls, were used. Results One person with alternating hemiplegia tested during the onset of a hemiplegic attack showed progressively diminishing motor cortex excitability until no response could be evoked; a second person tested during a prolonged bilateral hemiplegic attack showed unusually low excitability. Three people tested between attacks showed asymptomatic variation in cortical excitability, not seen in controls. Paired pulse paradigms, which probe intracortical inhibitory and excitatory circuits, gave results similar to controls. Conclusions We report symptomatic and asymptomatic fluctuations in motor cortex excitability in people with alternating hemiplegia of childhood, not seen in controls. We propose that such fluctuations underlie hemiplegic attacks, and speculate that the asymptomatic fluctuation we detected may be useful as a biomarker for disease activity. PMID:26999520

  18. An NCN-pincer ligand dysprosium single-ion magnet showing magnetic relaxation via the second excited state

    PubMed Central

    Guo, Yun-Nan; Ungur, Liviu; Granroth, Garrett E.; Powell, Annie K.; Wu, Chunji; Nagler, Stephen E.; Tang, Jinkui; Chibotaru, Liviu F.; Cui, Dongmei

    2014-01-01

    Single-molecule magnets are compounds that exhibit magnetic bistability purely of molecular origin. The control of anisotropy and suppression of quantum tunneling to obtain a comprehensive picture of the relaxation pathway manifold, is of utmost importance with the ultimate goal of slowing the relaxation dynamics within single-molecule magnets to facilitate their potential applications. Combined ab initio calculations and detailed magnetization dynamics studies reveal the unprecedented relaxation mediated via the second excited state within a new DyNCN system comprising a valence-localized carbon coordinated to a single dysprosium(III) ion. The essentially C2v symmetry of the DyIII ion results in a new relaxation mechanism, hitherto unknown for mononuclear DyIII complexes, opening new perspectives for means of enhancing the anisotropy contribution to the spin-relaxation barrier. PMID:24969218

  19. Magneto-Photoluminescence Based on Two-Photon Excitation in Lanthanide-Doped Up-Conversion Crystal Particles.

    PubMed

    Xu, Hengxing; Qin, Wei; Li, Mingxing; Wu, Ting; Hu, Bin

    2017-02-20

    Experimental studies on magneto-photoluminescence based on two-photon excitation in up-conversion Y2 O2 S:Er, Yb crystal particles are reported. It is found that the up-conversion photoluminescence generated by two-photon excitation exhibits magnetic field effects at room temperature, leading to a two-photon excitation-induced magneto-photoluminescence, when the two-photon excitation exceeds the critical intensity. By considering the spin selection rule in electronic transitions, it is proposed that spin-antiparallel and spin-parallel transition dipoles with spin mixing are accountable for the observed magneto-photoluminescence. Specifically, the two-photon excitation generates spin-antiparallel electric dipoles between (4) S3/2 -(4) I15/2 in Er(3+) ions. The antiparallel spins are conserved by exchange interaction within dipoles. When the photoexcitation exceeds the critical intensity, the Coulomb screening can decrease the exchange interaction. Consequently, the spin-orbital coupling can partially convert the antiparallel dipoles into parallel dipoles, generating a spin mixing. Eventually, the populations between antiparallel and parallel dipoles reach an equilibrium established by the competition between exchange interaction and spin-orbital coupling. Applying a magnetic field can break the equilibrium by disturbing spin mixing through introducing spin precessions, changing the spin populations on antiparallel and parallel dipoles and leading to the magneto-photoluminescence. Therefore, spin-dependent transition dipoles present a convenient mechanism to realize magneto-photoluminescence in multiphoton up-conversion crystal particles.

  20. X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

    DOE PAGES

    Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; ...

    2016-07-06

    We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (~6 to 300 K) and pressures (~0.1 to 17 GPa) studied. We have also investigated the electronic and magneticmore » excitations in single-crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high-resolution Ir L-3-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ~3-5 eV, spin-orbit excitations at ~ 0.5-1 eV, and broad low-lying excitations below ~0.15 eV. In single-crystal samples of "Eu-rich" Eu2Ir2O7 (found to possess an actual stoichiometry of Eu2.18Ir1.82O7.06) we observe highly damped magnetic excitations at ~45 meV, which display significant momentum dependence. Here, we compare these results with recent dynamical structure factor calculations« less

  1. Experimental observation of multiple-Q states for the magnetic skyrmion lattice and skyrmion excitations under a zero magnetic field

    NASA Astrophysics Data System (ADS)

    Nagao, Masahiro; So, Yeong-Gi; Yoshida, Hiroyuki; Yamaura, Kazunari; Nagai, Takuro; Hara, Toru; Yamazaki, Atsushi; Kimoto, Koji

    2015-10-01

    Model calculations indicate that the magnetic skyrmion lattice (SkL) is represented by a superposition of three spin helices at an angle of 120∘ to each other, the so-called triple-Q state. Using Lorentz transmission electron microscopy, we investigated the relationship between the SkL and the helix in FeGe thin films. After the magnetic field is removed, the ordered skyrmions are trapped inside helimagnetic domain walls (HDWs) where the different helical Q vectors are encountered. In situ observation revealed an unexpected topological excitation under such a zero-field state: skyrmions are spontaneously formed at HDWs.

  2. Vertical flows and structures excited by magnetic activity in the Galactic center region

    NASA Astrophysics Data System (ADS)

    Kakiuchi, Kensuke; Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji

    2017-01-01

    Various observations show peculiar features in the Galactic Center region, such as loops and filamentary structure. It is still unclear how such characteristic features are formed. Magnetic field is believed to play very important roles in the dynamics of gas in the Galaxy Center. Suzuki et al. (2015) performed a global magneto-hydrodynamical simulation focusing on the Galactic Center with an axisymmetric gravitational potential and claimed that non-radial motion is excited by magnetic activity. We further analyzed their simulation data and found that vertical motion is also excited by magnetic activity. In particular, fast down flows with speed of ~100 km/s are triggered near the footpoint of magnetic loops that are buoyantly risen by Parker instability. These downward flows are accelerated by the vertical component of the gravity, falling along inclined field lines. As a result, the azimuthal and radial components of the velocity are also excited, which are observed as high velocity features in a simulated position-velocity diagram. Depending on the viewing angle, these fast flows will show a huge variety of characteristic features in the position-velocity diagram.

  3. The Investigation of the Process of Magnetic Domain Nucleation and Growth Under Microwave Excitation.

    NASA Astrophysics Data System (ADS)

    Dong, Jie-Lin

    Two experiments designed to investigate the mechanism of magnetic domain generation under the excitation of a localized microwave field are performed. The domain observation were made with a high speed optical sampling microscope system. The samples were magnetic garnet films with the composition Y_{1.92}Sm _{0.1}Ca_ {0.98}Fe_{4.02} Ge_{0.98}O _{12}. The first experiment related to the observation of the process of magnetic bubble generation by microwave excitation. The dependence of the microwave power threshold for bubble generation on experimental conditions such as microwave frequency, microwave plus width, DC bias field, etc. is reported. It was found that the magnetization in the area driven by the strong microwave field responds rather noncoherently. Nucleation centers are formed first. Under appropriate conditions these centers may enlarge to a full size bubble. The second experiment related to magnetic bubble collapse both with and without an applied local microwave field. It was performed in order to obtain information on the pressure on the domain wall. To explain the experimental results, the analysis of bubble domain wall motion by Callen and Josephs has been modified by introducing a non-linear velocity-drive characteristic. In the case of no microwave excitation, good fit between the theory and the experimental data then is obtained. A model applicable when microwave field is present was made based on "dipolar pressure" and "intrinsic pressure" microwave effects. However, some discrepancies exist between the theory and experimental results. A two-dimensional tile matrix system was used to model domain nucleation and growth under microwave excitation. Some preliminary computer simulation results based on this model are obtained. These results are matched with the experimental observations qualitatively. For further quantitative comparison between the theory and experiment, more work has to be done.

  4. Emergence of nontrivial magnetic excitations in a spin-liquid state of kagomé volborthite

    PubMed Central

    Watanabe, Daiki; Sugii, Kaori; Shimozawa, Masaaki; Suzuki, Yoshitaka; Yajima, Takeshi; Ishikawa, Hajime; Hiroi, Zenji; Shibauchi, Takasada; Matsuda, Yuji; Yamashita, Minoru

    2016-01-01

    When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly correlated spins fluctuate down to very low temperatures, are prominent examples of such quantum states. SL states often exhibit exotic physical properties, but the precise nature of the elementary excitations behind such phenomena remains entirely elusive. Here, we use thermal Hall measurements that can capture the unexplored property of the elementary excitations in SL states, and report the observation of anomalous excitations that may unveil the unique features of the SL state. Our principal finding is a negative thermal Hall conductivity κxy which the charge-neutral spin excitations in a gapless SL state of the 2D kagomé insulator volborthite Cu3V2O7(OH)2⋅2H2O exhibit, in much the same way in which charged electrons show the conventional electric Hall effect. We find that κxy is absent in the high-temperature paramagnetic state and develops upon entering the SL state in accordance with the growth of the short-range spin correlations, demonstrating that κxy is a key signature of the elementary excitation formed in the SL state. These results suggest the emergence of nontrivial elementary excitations in the gapless SL state which feel the presence of fictitious magnetic flux, whose effective Lorentz force is found to be less than 1/100 of the force experienced by free electrons. PMID:27439874

  5. Magnetic and Orbital Excitations in Sr3CuIrO6

    NASA Astrophysics Data System (ADS)

    Hill, J. P.; Liu, X.; Dean, M.; Yin, W.; Tsvelik, A.; Kim, J.; Casa, D.; Upton, M. H.; Gretarsson, H.; Kim, Y.-J.; Qi, T.; Cao, G.; Hozoi, L.; Katukuri, V.; Brink, J. V. D.

    2012-02-01

    We report resonant inelastic x-ray scattering studies of the one-dimensional Sr3CuIrO6 at the Ir L3 edge, with δE=40 meV. At high energies, we find peaks at 0.6 eV, 0.9 eV, 3 eV, 4 eV and 6 eV. These peaks are non-dispersive, well-defined excitations. On the basis of quantum chemistry calculations, we are able to identify the first two as excitations within the t2g manifold and the next two as between the t2g and eg manifolds, together with charge transfer excitations from the O 2p to the Ir 5d. The 6 eV feature is another t2g - eg excitation. From these we are able to determine both the spin-orbit and non-cubic crystal field splittings. We find that they are of comparable strength. In addition, magnetic excitations are observed, corresponding to excitations of the j1/2 isospin. We find these are highly dispersive along the chain direction with a bandwidth of 20 meV and a gap of 30 meV. These results allow a complete modeling of the spin and orbital degrees of freedom in this model compound and we conclude an atomic, spin-orbit coupled description works well.

  6. Emergence of nontrivial magnetic excitations in a spin-liquid state of kagomé volborthite.

    PubMed

    Watanabe, Daiki; Sugii, Kaori; Shimozawa, Masaaki; Suzuki, Yoshitaka; Yajima, Takeshi; Ishikawa, Hajime; Hiroi, Zenji; Shibauchi, Takasada; Matsuda, Yuji; Yamashita, Minoru

    2016-08-02

    When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly correlated spins fluctuate down to very low temperatures, are prominent examples of such quantum states. SL states often exhibit exotic physical properties, but the precise nature of the elementary excitations behind such phenomena remains entirely elusive. Here, we use thermal Hall measurements that can capture the unexplored property of the elementary excitations in SL states, and report the observation of anomalous excitations that may unveil the unique features of the SL state. Our principal finding is a negative thermal Hall conductivity [Formula: see text] which the charge-neutral spin excitations in a gapless SL state of the 2D kagomé insulator volborthite Cu3V2O7(OH)2[Formula: see text]2H2O exhibit, in much the same way in which charged electrons show the conventional electric Hall effect. We find that [Formula: see text] is absent in the high-temperature paramagnetic state and develops upon entering the SL state in accordance with the growth of the short-range spin correlations, demonstrating that [Formula: see text] is a key signature of the elementary excitation formed in the SL state. These results suggest the emergence of nontrivial elementary excitations in the gapless SL state which feel the presence of fictitious magnetic flux, whose effective Lorentz force is found to be less than 1/100 of the force experienced by free electrons.

  7. Chaos of energetic positron orbits in a dipole magnetic field and its potential application to a new injection scheme

    NASA Astrophysics Data System (ADS)

    Saitoh, H.; Yoshida, Z.; Yano, Y.; Nishiura, M.; Kawazura, Y.; Horn-Stanja, J.; Pedersen, T. Sunn

    2016-10-01

    We study the behavior of high-energy positrons emitted from a radioactive source in a magnetospheric dipole field configuration. Because the conservation of the first and second adiabatic invariants is easily destroyed in a strongly inhomogeneous dipole field for high-energy charged particles, the positron orbits are nonintegrable, resulting in chaotic motions. In the geometry of a typical magnetospheric levitated dipole experiment, it is shown that a considerable ratio of positrons from a 22Na source, located at the edge of the confinement region, has chaotic long orbit lengths before annihilation. These particles make multiple toroidal circulations and form a hollow toroidal positron cloud. Experiments with a small 22Na source in the Ring Trap 1 (RT-1) device demonstrated the existence of such long-lived positrons in a dipole field. Such a chaotic behavior of high-energy particles is potentially applicable to the formation of a dense toroidal positron cloud in the strong-field region of the dipole field in future studies.

  8. Chaos of energetic positron orbits in a dipole magnetic field and its potential application to a new injection scheme.

    PubMed

    Saitoh, H; Yoshida, Z; Yano, Y; Nishiura, M; Kawazura, Y; Horn-Stanja, J; Pedersen, T Sunn

    2016-10-01

    We study the behavior of high-energy positrons emitted from a radioactive source in a magnetospheric dipole field configuration. Because the conservation of the first and second adiabatic invariants is easily destroyed in a strongly inhomogeneous dipole field for high-energy charged particles, the positron orbits are nonintegrable, resulting in chaotic motions. In the geometry of a typical magnetospheric levitated dipole experiment, it is shown that a considerable ratio of positrons from a ^{22}Na source, located at the edge of the confinement region, has chaotic long orbit lengths before annihilation. These particles make multiple toroidal circulations and form a hollow toroidal positron cloud. Experiments with a small ^{22}Na source in the Ring Trap 1 (RT-1) device demonstrated the existence of such long-lived positrons in a dipole field. Such a chaotic behavior of high-energy particles is potentially applicable to the formation of a dense toroidal positron cloud in the strong-field region of the dipole field in future studies.

  9. Direct-Drive Synchronous Generators with Excitation from Strontium-Ferrite Magnets: Efficiency Improvement

    NASA Astrophysics Data System (ADS)

    Serebryakov, A.; Levin, N.; Sokolov, A.

    2012-01-01

    The authors consider the possibility to raise the specific power of synchronous generators with excitation from inexpensive permanent magnets. For this purpose, it is proposed to use tooth-wise windings and permanent magnets based on inexpensive magneto-hard material, e.g. strontium-ferrite. The magnets are to be placed between the rotor teeth, the alternate polarity of which is facing the air-gap. This provides a simpler and cheaper technology of making such a generator and improves its reliability. The proposed rational bevelling of the stator teeth not only raises the specific power of the generator but also reduces the level of noise and vibrations, extends the longevity of the magnets and bearings as well as facilitates the starting torque of the electric machine, e.g. if it is employed as wind generator.

  10. Temperature Dependence of Magnetic Excitations: Terahertz Magnons above the Curie Temperature

    NASA Astrophysics Data System (ADS)

    Qin, H. J.; Zakeri, Kh.; Ernst, A.; Kirschner, J.

    2017-03-01

    When an ordered spin system of a given dimensionality undergoes a second order phase transition, the dependence of the order parameter, i.e., magnetization on temperature, can be well described by thermal excitations of elementary collective spin excitations (magnons). However, the behavior of magnons themselves, as a function of temperature and across the transition temperature TC, is an unknown issue. Utilizing spin-polarized high resolution electron energy loss spectroscopy, we monitor the high-energy (terahertz) magnons, excited in an ultrathin ferromagnet, as a function of temperature. We show that the magnons' energy and lifetime decrease with temperature. The temperature-induced renormalization of the magnons' energy and lifetime depends on the wave vector. We provide quantitative results on the temperature-induced damping and discuss the possible mechanism, e.g., multimagnon scattering. A careful investigation of physical quantities determining the magnons' propagation indicates that terahertz magnons sustain their propagating character even at temperatures far above TC.

  11. Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

    PubMed Central

    Van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

    2016-01-01

    Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

  12. Possible Itinerant Moment Contributions to the Magnetic Excitations in Gd, Studied by Neutron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Granroth, G. E.; Aczel, A. A.; Fernandez-Baca, J. A.; Nagler, S. E.

    2013-03-01

    Many experimental features in magnetic superconductors are also present when these complex materials are in the normal state. Therefore studies of simpler itinerant magnets may help provide understanding of these phenomena. We chose to study Gd as it is has an ~ 0 . 6μB itinerant moment in addition to a ~ 7 . 0μB localized moment. The SEQUOIA spectrometer, at the Spallation Neutron Source at Oak Ridge National Laboratory, was used in fine resolution mode with Ei=50 meV neutrons, to measure the magnetic excitations in a 12 gm 160Gd single crystal. The crystal was mounted with the h 0 l plane horizontal and rotated around the vertical axis to map out the excitations. The measured magnetic structure factor for the acoustic modes in the hh 0 direction has an intensity step at h ~ 0 . 3 . Electronic band structure calculations (W. M. Temmerman and P. A. Sterne, J. Phys: Condes. Matter,2, 5529 (1990)) show this Q position to be near several band crossings of the Fermi surface. A detailed analysis, including instrumental resolution, is presented to clarify any relationship between the magnetic structure factor and the electronic band structure. This work was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

  13. Tunable short-wavelength spin wave excitation from pinned magnetic domain walls.

    PubMed

    Van de Wiele, Ben; Hämäläinen, Sampo J; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

    2016-02-17

    Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors.

  14. Elementary excitations of a Bose-Einstein condensate in an effective magnetic field

    SciTech Connect

    Murray, D. R.; Barnett, Stephen M.; Oehberg, P.; Gomila, Damia

    2007-11-15

    We calculate the low-energy elementary excitations of a Bose-Einstein condensate in an effective magnetic field. The field is created by the interplay between light beams carrying orbital angular momentum and the trapped atoms [G. Juzeliunas et al., Phys. Rev. A 71, 053614 (2005)]. We examine the role of the homogeneous magnetic field, familiar from studies of rotating condensates, and also investigate spectra for vector potentials with a more general radial dependence. We discuss the instabilities which arise and how these may be manifested.

  15. A function of the magnetocaloric effect in a magnetic fluid

    SciTech Connect

    Polunin, V.M.

    1986-01-01

    This paper examines a plane-parallel layer of magnetic fluid (MF) contacting the tmosphere. A relation which determines the density of the fluid with respect to the magnetic field strength is presented in the case of isothermal magnetization. The magnetocaloric effect is discussed which performs the function of one of the possible mechanisms of electromagnitic excitation of elastic vibrations in the MF. Two other mechanisms are discussed: magnetostriction and dipole-dipole.

  16. Modelling an arbitrarily oriented magnetic dipole over a homogeneous half-space for a rapid topographic correction of airborne EM data

    NASA Astrophysics Data System (ADS)

    Guillemoteau, Julien; Sailhac, Pascal; Behaegel, Mickael

    2015-10-01

    Most airborne electromagnetic (EM) processing programs assume a flat ground surface. However, in mountainous areas, the system can be at an angle with regard to the ground. As the system is no longer parallel to the ground surface, the measured magnetic field has to be corrected and the ground induced eddy current has to be modelled in a better way when performing a very fine interpretation of the data. We first recall the theoretical background for the modelling of a magnetic dipole source and study it in regard to the case of an arbitrarily oriented magnetic dipole. We show in particular how transient central loop helicopter borne data are influenced by this inclination. The result shows that the effect of topography on airborne EM is more important at early time windows and for systems using a short cut-off source. In this paper, we suggest that an estimate be made off the locally averaged inclination of the system to the ground and then to correct the data for this before inverting it (whether the inversion assumes a flat 1D, 2D or 3D sub-surface). Both 1D and 2D inversions are applied to synthetic and real data sets with such a correction. The consequence on the ground imaging is small for slopes with an angle less than 25° but the correction factor can be useful for improving the estimation of depths in mountainous areas.

  17. Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr1 -xLax)3Ir2O7

    NASA Astrophysics Data System (ADS)

    Lu, Xingye; McNally, D. E.; Moretti Sala, M.; Terzic, J.; Upton, M. H.; Casa, D.; Ingold, G.; Cao, G.; Schmitt, T.

    2017-01-01

    We use resonant elastic and inelastic x-ray scattering at the Ir-L3 edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr1 -xLax )3Ir2 O7 (0 ≤x ≤0.065 ). With increasing doping x , the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x =0 to 0.05, followed by a transition to two-dimensional short range order between x =0.05 and 0.065. Because of the interactions between the Jeff=1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr1 -xLax )3Ir2 O7 into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the Jeff=1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.

  18. Plasmonic localized heating beyond the diffraction limit via magnetic polariton excitation

    NASA Astrophysics Data System (ADS)

    Alshehri, Hassan; Ying, Xiaoyan; Wang, Hao; Wang, Liping

    2016-09-01

    Optical localized heating in the nanoscale has recently attracted great attention due to its unique small hot spot size with high energy. However, the hot spot size is conventionally constrained by the diffraction limit. Plasmonic localized heating can provide solutions to this limitation in nanoscale patterning, cancer treatment, and data storage. Plasmonic approaches to overcome the diffraction limit in hot spot size have mainly utilized the excitation of surface plasmon or localized surface plasmon resonance. However, achieving plasmonic localized heating by the excitation of magnetic polariton has not been researched extensively yet. In this work, we numerically investigated the optical response of a nanoscale metamaterial composed of a gold nanowire array and a gold film separated by an ultrathin polymer spacer using ANSYS High Frequency Structural Simulator. A strong absorption peak at the wavelength of 760 nm was exhibited, and the underlying physical mechanism for the strong absorption was verified via the local electromagnetic field distribution to be magnetic resonance excitation. An inductor-capacitor circuit model was used to predict the magnetic resonance wavelength and compare with the numerical results for varied geometrical parameters. Volume loss density due to the strong local optical energy confinement was transferred as heat generation to an ANSYS thermal solver to obtain the local temperature profile. The steady state temperature profile shows an average temperature of 145 °C confined in a local area as small as 33 nm within the spacer, with a full-width at half-maximum of 50 nm along the x-direction. Moreover, the temperature rise from ambient drops to half its maximum value at a distance of 5 nm from the top of the spacer along the z-direction. This clearly demonstrates plasmonic localized heating beyond the diffraction limit via magnetic polariton excitation. Furthermore, the transient temperature profile shows that the system reached

  19. Excitation of dayside chorus waves due to magnetic field line compression in response to interplanetary shocks

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Li, Wen; Thorne, Richard M.; Bortnik, Jacob; Ma, Qianli; An, Xin; Zhang, Xiao-jia; Angelopoulos, Vassilis; Ni, Binbin; Gu, Xudong; Fu, Song; Zhao, Zhengyu

    2015-10-01

    The excitation of magnetospheric whistler-mode chorus in response to interplanetary (IP) shocks is investigated using wave data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. As an example, we show a typical chorus wave excitation following an IP shock event that was observed by THEMIS in the postnoon sector near the magnetopause on 3 August 2010. We then analyze characteristic changes during this event and perform a survey of similar events during the period 2008-2014 using the THEMIS and OMNI data set. Our statistical analysis demonstrates that the chorus wave excitation/intensification in response to IP shocks occurs only at high L shells (L > 8) on the dayside. We analyzed the variations of magnetic curvature following the arrival of the IP shock and found that IP shocks lead to more homogeneous background magnetic field configurations in the near-equatorial dayside magnetosphere; and therefore, the threshold of nonlinear chorus wave growth is likely to be reduced, favoring chorus wave generation. Our results provide the observational evidence to support the concept that the geomagnetic field line configuration plays a key role in the excitation of dayside chorus.

  20. Plasmonic local heating beyond diffraction limit by the excitation of magnetic polariton

    NASA Astrophysics Data System (ADS)

    Alshehri, Hassan; Wang, Hao; Ma, Yanchao; Wang, Liping

    2015-08-01

    In recent years, optical local heating in the nanoscale has attracted great attention due to its unique features of small hot spot size and high energy density. Plasmonic local heating can provide solutions to several challenges in data storage and cancer treatment. Research conducted in this field to achieve plasmonic local heating has mainly utilized the excitation of localized surface plasmon (LSP) or surface plasmon resonance (SPR). However, achieving plasmonic local heating by the excitation of magnetic polariton (MP) has not been researched extensively yet. We numerically investigate the optical response of a nanostructure composed of a gold nanowire on a gold surface separated by a polymer spacer using the ANSYS High Frequency Structural Simulator (HFSS). The structure exhibits a strong absorption peak at the wavelength of 750 nm, and the underlying physical mechanism is verified by the local electromagnetic field distribution to be the magnetic resonance excitation. By incorporating the volume loss density due to the strong local optical energy confinement as the heat generation, nanoscale temperature distribution within the structure is numerically obtained with a thermal solver after assigning proper boundary conditions. The results show a maximum temperature of 158.5°C confined in a local area on the order of 35 nm within the ultrathin polymer layer, which clearly demonstrates the plasmonic local heating effect beyond diffraction limit by excitation of MP.

  1. Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Guarise, M.; Piazza, B. Dalla; Berger, H.; Giannini, E.; Schmitt, T.; Rønnow, H. M.; Sawatzky, G. A.; van den Brink, J.; Altenfeld, D.; Eremin, I.; Grioni, M.

    2014-12-01

    The high-Tc cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin waves—magnons—of the antiferromagnetic insulating parent compounds, suggesting that magnons may survive in damped, broadened form throughout the phase diagram. Here we show by resonant inelastic X-ray scattering on Bi2Sr2CaCu2O8+δ (Bi-2212) that the analogy with spin waves is only partial. The magnon-like features collapse along the nodal direction in momentum space and exhibit a photon energy dependence markedly different from the Mott-insulating case. These observations can be naturally described by the continuum of charge and spin excitations of correlated electrons. The persistence of damped magnons could favour scenarios for superconductivity built from quasiparticles coupled to spin fluctuations. However, excitation spectra composed of particle-hole excitations suggest that superconductivity emerges from a coherent treatment of electronic spin and charge in the form of quasiparticles with very strong magnetic correlations.

  2. Topological honeycomb magnon Hall effect: A calculation of thermal Hall conductivity of magnetic spin excitations

    NASA Astrophysics Data System (ADS)

    Owerre, S. A.

    2016-07-01

    Quite recently, the magnon Hall effect of spin excitations has been observed experimentally on the kagome and pyrochlore lattices. The thermal Hall conductivity κxy changes sign as a function of magnetic field or temperature on the kagome lattice, and κxy changes sign upon reversing the sign of the magnetic field on the pyrochlore lattice. Motivated by these recent exciting experimental observations, we theoretically propose a simple realization of the magnon Hall effect in a two-band model on the honeycomb lattice. The magnon Hall effect of spin excitations arises in the usual way via the breaking of inversion symmetry of the lattice, however, by a next-nearest-neighbour Dzyaloshinsky-Moriya interaction. We find that κxy has a fixed sign for all parameter regimes considered. These results are in contrast to the Lieb, kagome, and pyrochlore lattices. We further show that the low-temperature dependence on the magnon Hall conductivity follows a T2 law, as opposed to the kagome and pyrochlore lattices. These results suggest an experimental procedure to measure thermal Hall conductivity within a class of 2D honeycomb quantum magnets and ultracold atoms trapped in a honeycomb optical lattice.

  3. Magnetic Excitations in the Stacked Quantum Magnets NaNiO2 and LiNiO2

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gaulin, B. D.; Ruff, J. P. C.; Ross, K. A.; van Gastel, G. J.; Abernathy, D. L.; Stone, M. B.

    2009-03-01

    NaNiO2 and LiNiO2 are isostructural stacked triangular lattice quantum magnets, in which magnetism is conventionally thought to arise due to spin 1/2 moments carried by Ni^3+ ions. Surprisingly, while NaNiO2 undergoes a cooperative Jahn-Teller transition at 480K and magnetically orders below TN ˜ 23K, LiNiO2 undergoes a glass transition at Tg ˜ 9K and remains disordered down to the lowest measured temperatures. The absence of long-range magnetic order in LiNiO2 has been attributed to either geometric frustration caused by mixing of the Li and Ni sublattices, or orbital degeneracy due to the absence of a coherent Jahn-Teller distortion. We have performed time of flight neutron scattering measurements on polycrystalline samples of NaNiO2 and LiNiO2 using the wide Angular-Range Chopper Spectrometer (ARCS) at the SNS. Our measurements reveal previously unobserved magnetic excitations at relatively high energy transfers, which we associate with ferromagnetic spin waves mediated by in-plane interactions. We also find evidence of critical scattering in NaNiO2 near the magnetic phase transition at TN. These results will be compared with previous measurements collected using the DCS at NIST.

  4. Canard and mixed mode oscillations in an excitable glow discharge plasma in the presence of inhomogeneous magnetic field

    SciTech Connect

    Shaw, Pankaj Kumar Sekar Iyengar, A. N.

    2015-12-15

    We report on the experimental observation of canard orbit and mixed mode oscillations (MMOs) in an excitable glow discharge plasma induced by an external magnetic field perturbation using a bar magnet. At a small value of magnetic field, small amplitude quasiperiodic oscillations were excited, and with the increase in the magnetic field, large amplitude oscillations were excited. Analyzing the experimental results, it seems that the magnetic field could be playing the role of noise for such nonlinear phenomena. It is observed that the noise level increases with the increase in magnetic field strength. The experimental results have also been corroborated by a numerical simulation using a FitzHugh-Nagumo like macroscopic model derived from the basic plasma equations and phenomenology, where the noise has been included to represent the internal plasma noise. This macroscopic model shows MMO in the vicinity of the canard point when an external noise is added.

  5. Enhanced photoelectric detection of NV magnetic resonances in diamond under dual-beam excitation

    NASA Astrophysics Data System (ADS)

    Bourgeois, E.; Londero, E.; Buczak, K.; Hruby, J.; Gulka, M.; Balasubramaniam, Y.; Wachter, G.; Stursa, J.; Dobes, K.; Aumayr, F.; Trupke, M.; Gali, A.; Nesladek, M.

    2017-01-01

    The core issue for the implementation of NV center qubit technology is a sensitive readout of the NV spin state. We present here a detailed theoretical and experimental study of NV center photoionization processes, used as a basis for the design of a dual-beam photoelectric method for the detection of NV magnetic resonances (PDMR). This scheme, based on NV one-photon ionization, is significantly more efficient than the previously reported single-beam excitation scheme. We demonstrate this technique on small ensembles of ˜10 shallow NVs implanted in electronic grade diamond (a relevant material for quantum technology), on which we achieve a cw magnetic resonance contrast of 9%—three times enhanced compared to previous work. The dual-beam PDMR scheme allows independent control of the photoionization rate and spin magnetic resonance contrast. Under a similar excitation, we obtain a significantly higher photocurrent, and thus an improved signal-to-noise ratio, compared to single-beam PDMR. Finally, this scheme is predicted to enhance magnetic resonance contrast in the case of samples with a high proportion of substitutional nitrogen defects, and could therefore enable the photoelectric readout of single NV spins.

  6. Resonantly excited precession motion of three-dimensional vortex core in magnetic nanospheres [corrected].

    PubMed

    Kim, Sang-Koog; Yoo, Myoung-Woo; Lee, Jehyun; Lee, Ha-Youn; Lee, Jae-Hyeok; Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D

    2015-06-16

    We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ〈mΓ〉 is the effective gyromagnetic ratio in collective vortex dynamics, with the gyromagnetic ratio γ and the average magnetization component 〈mΓ〉 of the ground-state vortex in the core direction. Fitting to the micromagnetic simulation data for 〈mΓ〉 yields a simple explicit form of 〈mΓ〉 ≈ (73.6 ± 3.4)(lex/2R)(2.20±0.14), where lex is the exchange length of a given material. This dynamic behavior might serve as a foundation for potential bio-applications of size-specific resonant excitation of magnetic vortex-state nanoparticles, for example, magnetic particle resonance imaging.

  7. Orientation of emitting dipoles of chlorophyll A in thylakoids: considerations on the orientation factor in vivo.

    PubMed Central

    Garab, G I; Kiss, J G; Mustárdy, L A; Michel-Villaz, M

    1981-01-01

    Orientation angles of five emitting dipoles of chlorophyll a in thylakoids were estimated from low temperature fluorescence polarization ratio spectra of magnetically oriented chloroplasts. A simple expression is given also for the evaluation of data from linear dichroism measurements. It is shown that the Qy dipoles of chlorophylls lie more in the plane of the membranes and span a larger angular interval than was previously thought. Values for the orientation factor are calculated using various models corresponding to different degrees of local order of the Qy dipoles of chlorophylls in the thylakoid. We show that the characteristic orientation pattern of the Qy dipoles of chlorophylls in the membrane, i.e., increasing dichroism toward longer wavelengths, may favour energy transfer between the antenna chlorophylls as well as funnel the excitation energy into the reaction centers. Images FIGURE 1 FIGURE 4 PMID:7248470

  8. Femtosecond switching of magnetism via strongly correlated spin-charge quantum excitations.

    PubMed

    Li, Tianqi; Patz, Aaron; Mouchliadis, Leonidas; Yan, Jiaqiang; Lograsso, Thomas A; Perakis, Ilias E; Wang, Jigang

    2013-04-04

    The technological demand to push the gigahertz (10(9) hertz) switching speed limit of today's magnetic memory and logic devices into the terahertz (10(12) hertz) regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states--femtosecond-laser-excited coherence between electronic states can switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of correlated materials: for example, manganites exhibiting colossal magneto-resistance suitable for applications. Here we show femtosecond (10(-15) seconds) photo-induced switching from antiferromagnetic to ferromagnetic ordering in Pr0.7Ca0.3MnO3, by observing the establishment (within about 120 femtoseconds) of a huge temperature-dependent magnetization with photo-excitation threshold behaviour absent in the optical reflectivity. The development of ferromagnetic correlations during the femtosecond laser pulse reveals an initial quantum coherent regime of magnetism, distinguished from the picosecond (10(-12) seconds) lattice-heating regime characterized by phase separation without threshold behaviour. Our simulations reproduce the nonlinear femtosecond spin generation and underpin fast quantum spin-flip fluctuations correlated with coherent superpositions of electronic states to initiate local ferromagnetic correlations. These results merge two fields, femtosecond magnetism in metals and band insulators, and non-equilibrium phase transitions of strongly correlated electrons, in which local interactions exceeding the kinetic energy produce a complex balance of competing orders.

  9. Progress toward measuring the 6S1/2 <--> 5D3/2 magnetic-dipole transition moment in Ba+

    NASA Astrophysics Data System (ADS)

    Williams, Spencer; Jayakumar, Anupriya; Hoffman, Matthew; Blinov, Boris; Fortson, Norval

    2015-05-01

    We report the latest results from our effort to measure the magnetic-dipole transition moment (M1) between the 6S1 / 2 and 5D3 / 2 manifolds in Ba+. We describe a new technique for calibrating view-port birefringence and how we will use it to enhance the M1 signal. To access the transition moment we use a variation of a previously proposed technique that allows us to isolate the magnetic-dipole coupling from the much larger electric-quadrupole coupling in the transition rates between particular Zeeman sub-levels. Knowledge of M1 is crucial for a parity-nonconservation experiment in the ion where M1 will be a leading source of systematic errors. No measurement of this M1 has been made in Ba+, however, there are three calculations that predict it to be 80 ×10-5μB, 22 ×10-5μB, and 17 ×10-5μB. A precise measurement may help resolve this theoretical discrepancy which originates from their different estimations of many-body effects. Supported by NSF Grant No. 09-06494F.

  10. Classical and quantum interaction of the dipole

    PubMed

    Anandan

    2000-08-14

    A unified and fully relativistic treatment of the interaction of the electric and magnetic dipole moments of a particle with the electromagnetic field is given. New forces on the particle due to the combined effect of electric and magnetic dipoles are obtained. Several new experiments are proposed, which include observation of topological phase shifts.

  11. New aspects of the magnetic excitations in HoCo2

    NASA Astrophysics Data System (ADS)

    Castets, A.; Gignoux, D.; Hennion, B.

    1982-01-01

    We have obtained new results about the magnetic excitation spectrum of HoCo2 using inelastic neutron scattering. It has been possible to observe at 6 K a well-defined cobalt excitation mode up to 14 THz. The application of a magnetic field along the easy magnetization axis has revealed the longitudinal character of the excitation at 2 THz observed at 6 K. New modes below and above the rotation temperature have been measured. These results have been analyzed in a Green's-function formalism using the random-phase approximation to determine the crystalline electric field (CEF) and the exchange parameters. Despite the use of an extra quadrupolar term for the crystalline field it has not been possible to get a satisfactory agreement for the dispersion curves obtained, together with the macroscopic measurements. However, the values obtained W=0.2983 K and x=-0.4839 for the CEF parameters are in agreement with those determined by other authors. The exchange parameters have been determined as JHo-Ho=0+/-0.0005 THz, JHo-Co=-0.07 THz, and JCo-Co=9 THz. The main discrepancy concerns JHo-Co which may be determined from the gap of the cobalt mode or from the molecular field when the CEF transition levels are fitted regardless of the cobalt mode. The discrepancy suggests that it might be necessary to take into account a mixture of 3d and 4f magnetism at the very level of the exchange mechanism, including the itinerant character of the 3d electrons.

  12. Combination of Static Magnetic Fields and Peripheral Nerve Stimulation Can Alter Focal Cortical Excitability

    PubMed Central

    Nojima, Ippei; Koganemaru, Satoko; Mima, Tatsuya

    2016-01-01

    For clinical application of transcranial static magnetic stimulation (tSMS), it is important to achieve a focal target cortical stimulation. Previous study suggested that the associative stimulation combining non-invasive stimulation of the motor cortex (M1) and the peripheral nerve stimulation (PNS) may be useful to produce cortical excitability change. To test this hypothesis, we measured the M1 excitability and intracortical circuits by using transcranial magnetic stimulation (TMS) before and after the tSMS of short duration (5 min) combined with PNS. Thirty-three normal volunteers were participated; tSMS+PNS (n = 11), sham+PNS (n = 11), and tSMS alone (n = 11). We found the transient suppression of the motor-evoked potential (MEP) of the right abductor pollicis brevis (APB) muscle, but not of the abductor digiti minimi (ADM) muscle, when combining tSMS with PNS over median nerve at the wrist. The lack of suppressive effect on APB in tSMS alone with short duration is in accord with the previous observation. In addition, the tendency of transient enhancement of the short-latency intracortical inhibition was observed immediately after intervention in the tSMS±PNS group. These findings show that the combination of tSMS and PNS can induce the cortical excitability change in target cortical motor area and potentiate the suppression effect. PMID:27932966

  13. Dipole nanolaser

    NASA Astrophysics Data System (ADS)

    Protsenko, I. E.; Uskov, A. V.; Zaimidoroga, O. A.; Samoilov, V. N.; O'Reilly, E. P.

    2005-06-01

    A “dipole” laser is proposed consisting of a nanoparticle and a two-level system with population inversion. If the threshold conditions are fulfilled, the dipole interaction between the two-level system and the nanoparticle leads to coherent oscillations in the polarization of the particles, even in the absence of an external electromagnetic field. The emitted radiation has a dipolar distribution. It does not need an optical cavity, and has a very small volume, ˜0.1μm3 , which can be important for applications in microelectronics. Estimates of the threshold conditions are carried out for a dipole laser composed of a quantum dot and a silver nanoparticle.

  14. Fermion dipole moment and holography

    NASA Astrophysics Data System (ADS)

    Kulaxizi, Manuela; Rahman, Rakibur

    2015-12-01

    In the background of a charged AdS black hole, we consider a Dirac particle endowed with an arbitrary magnetic dipole moment. For non-zero charge and dipole coupling of the bulk fermion, we find that the dual boundary theory can be plagued with superluminal modes. Requiring consistency of the dual CFT amounts to constraining the strength of the dipole coupling by an upper bound. We briefly discuss the implications of our results for the physics of holographic non-Fermi liquids.

  15. Quantum electric-dipole liquid on a triangular lattice.

    PubMed

    Shen, Shi-Peng; Wu, Jia-Chuan; Song, Jun-Da; Sun, Xue-Feng; Yang, Yi-Feng; Chai, Yi-Sheng; Shang, Da-Shan; Wang, Shou-Guo; Scott, James F; Sun, Young

    2016-02-04

    Geometric frustration and quantum fluctuations may prohibit the formation of long-range ordering even at the lowest temperature, and therefore liquid-like ground states could be expected. A good example is the quantum spin liquid in frustrated magnets. Geometric frustration and quantum fluctuations can happen beyond magnetic systems. Here we propose that quantum electric-dipole liquids, analogues of quantum spin liquids, could emerge in frustrated dielectrics where antiferroelectrically coupled electric dipoles reside on a triangular lattice. The quantum paraelectric hexaferrite BaFe12O19 with geometric frustration represents a promising candidate for the proposed electric-dipole liquid. We present a series of experimental lines of evidence, including dielectric permittivity, heat capacity and thermal conductivity measured down to 66 mK, to reveal the existence of an unusual liquid-like quantum phase in BaFe12O19, characterized by itinerant low-energy excitations with a small gap. The possible quantum liquids of electric dipoles in frustrated dielectrics open up a fresh playground for fundamental physics.

  16. Quantum electric-dipole liquid on a triangular lattice

    NASA Astrophysics Data System (ADS)

    Shen, Shi-Peng; Wu, Jia-Chuan; Song, Jun-Da; Sun, Xue-Feng; Yang, Yi-Feng; Chai, Yi-Sheng; Shang, Da-Shan; Wang, Shou-Guo; Scott, James F.; Sun, Young

    2016-02-01

    Geometric frustration and quantum fluctuations may prohibit the formation of long-range ordering even at the lowest temperature, and therefore liquid-like ground states could be expected. A good example is the quantum spin liquid in frustrated magnets. Geometric frustration and quantum fluctuations can happen beyond magnetic systems. Here we propose that quantum electric-dipole liquids, analogues of quantum spin liquids, could emerge in frustrated dielectrics where antiferroelectrically coupled electric dipoles reside on a triangular lattice. The quantum paraelectric hexaferrite BaFe12O19 with geometric frustration represents a promising candidate for the proposed electric-dipole liquid. We present a series of experimental lines of evidence, including dielectric permittivity, heat capacity and thermal conductivity measured down to 66 mK, to reveal the existence of an unusual liquid-like quantum phase in BaFe12O19, characterized by itinerant low-energy excitations with a small gap. The possible quantum liquids of electric dipoles in frustrated dielectrics open up a fresh playground for fundamental physics.

  17. Quantum electric-dipole liquid on a triangular lattice

    PubMed Central

    Shen, Shi-Peng; Wu, Jia-Chuan; Song, Jun-Da; Sun, Xue-Feng; Yang, Yi-Feng; Chai, Yi-Sheng; Shang, Da-Shan; Wang, Shou-Guo; Scott, James F.; Sun, Young

    2016-01-01

    Geometric frustration and quantum fluctuations may prohibit the formation of long-range ordering even at the lowest temperature, and therefore liquid-like ground states could be expected. A good example is the quantum spin liquid in frustrated magnets. Geometric frustration and quantum fluctuations can happen beyond magnetic systems. Here we propose that quantum electric-dipole liquids, analogues of quantum spin liquids, could emerge in frustrated dielectrics where antiferroelectrically coupled electric dipoles reside on a triangular lattice. The quantum paraelectric hexaferrite BaFe12O19 with geometric frustration represents a promising candidate for the proposed electric-dipole liquid. We present a series of experimental lines of evidence, including dielectric permittivity, heat capacity and thermal conductivity measured down to 66 mK, to reveal the existence of an unusual liquid-like quantum phase in BaFe12O19, characterized by itinerant low-energy excitations with a small gap. The possible quantum liquids of electric dipoles in frustrated dielectrics open up a fresh playground for fundamental physics. PMID:26843363

  18. Excitation of propagating spin waves in ferromagnetic nanowires by microwave voltage-controlled magnetic anisotropy.

    PubMed

    Verba, Roman; Carpentieri, Mario; Finocchio, Giovanni; Tiberkevich, Vasil; Slavin, Andrei

    2016-04-26

    The voltage-controlled magnetic anisotropy (VCMA) effect, which manifests itself as variation of anisotropy of a thin layer of a conductive ferromagnet on a dielectric substrate under the influence of an external electric voltage, can be used for the development of novel information storage and signal processing devices with low power consumption. Here it is demonstrated by micromagnetic simulations that the application of a microwave voltage to a nanosized VCMA gate in an ultrathin ferromagnetic nanowire results in the parametric excitation of a propagating spin wave, which could serve as a carrier of information. The frequency of the excited spin wave is twice smaller than the frequency of the applied voltage while its amplitude is limited by 2 mechanisms: (i) the so-called "phase mechanism" described by the Zakharov-L'vov-Starobinets "S-theory" and (ii) the saturation mechanism associated with the nonlinear frequency shift of the excited spin wave. The developed extension of the "S-theory", which takes into account the second limitation mechanism, allowed us to estimate theoretically the efficiency of the parametric excitation of spin waves by the VCMA effect.

  19. Excitation of propagating spin waves in ferromagnetic nanowires by microwave voltage-controlled magnetic anisotropy

    PubMed Central

    Verba, Roman; Carpentieri, Mario; Finocchio, Giovanni; Tiberkevich, Vasil; Slavin, Andrei

    2016-01-01

    The voltage-controlled magnetic anisotropy (VCMA) effect, which manifests itself as variation of anisotropy of a thin layer of a conductive ferromagnet on a dielectric substrate under the influence of an external electric voltage, can be used for the development of novel information storage and signal processing devices with low power consumption. Here it is demonstrated by micromagnetic simulations that the application of a microwave voltage to a nanosized VCMA gate in an ultrathin ferromagnetic nanowire results in the parametric excitation of a propagating spin wave, which could serve as a carrier of information. The frequency of the excited spin wave is twice smaller than the frequency of the applied voltage while its amplitude is limited by 2 mechanisms: (i) the so-called “phase mechanism” described by the Zakharov-L’vov-Starobinets “S-theory” and (ii) the saturation mechanism associated with the nonlinear frequency shift of the excited spin wave. The developed extension of the “S-theory”, which takes into account the second limitation mechanism, allowed us to estimate theoretically the efficiency of the parametric excitation of spin waves by the VCMA effect. PMID:27113392

  20. Ordering and thermal excitations in dipolar coupled single domain magnet arrays (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Östman, Erik; Arnalds, Unnar; Kapaklis, Vassilios; Hjörvarsson, Björgvin

    2015-09-01

    For a small island of a magnetic material the magnetic state of the island is mainly determined by the exchange interaction and the shape anisotropy. Two or more islands placed in close proximity will interact through dipolar interactions. The state of a large system will thus be dictated by interactions at both these length scales. Enabling internal thermal fluctuations, e.g. by the choice of material, of the individual islands allows for the study of thermal ordering in extended nano-patterned magnetic arrays [1,2]. As a result nano-magnetic arrays represent an ideal playground for the study of physical model systems. Here we present three different studies all having used magneto-optical imaging techniques to observe, in real space, the order of the systems. The first study is done on a square lattice of circular islands. The remanent magnetic state of each island is a magnetic vortex structure and we can study the temperature dependence of the vortex nucleation and annihilation fields [3]. The second are long chains of dipolar coupled elongated islands where the magnetization direction in each island only can point in one of two possible directions. This creates a system which in many ways mimics the Ising model [4] and we can relate the correlation length to the temperature. The third one is a spin ice system where elongated islands are placed in a square lattice. Thermal excitations in such systems resemble magnetic monopoles [2] and we can investigate their properties as a function of temperature and lattice parameters. [1] V. Kapaklis et al., New J. Phys. 14, 035009 (2012) [2] V. Kapaklis et al., Nature Nanotech 9, 514(2014) [3] E. Östman et al.,New J. Phys. 16, 053002 (2014) [4] E. Östman et al.,Thermal ordering in mesoscopic Ising chains, In manuscript.