Perpendicular Component Of Magnetic Field Research Articles

Ferromagnetic Coating for Decreasingof Self-Magnetic Field Acting on HTS Tapes

The decreasing of critical current in the high-temperature tape superconductor (HTS) can be prevented by decreasing of the perpendicular component of self-magnetic field. The coating of this tape by the ferromagnetic material can deform the magnetic field around the HTS tape with flowing transport current. The present report contains the finite-element analysis of the effect of ferromagnetic coating near the HTS tape. The optimal configuration of the ferromagnetic coating for minimizing the perpendicular component of magnetic field was found. In present case, it reduces from 0.04 T to less than 0.01 T. The optimal shape of the coating contains the gap along the lateral side of the HTS tape. The influence of the twisting of the tape coated by ferromagnetic was also investigated. It was found that the difference between twisted and nontwisted cables was not large. The study was also performed for the stack of HTS tapes where neighbor tapes have the opposite direction of the transport current. It was found that the ferromagnetic coating and ribs make the magnetic field near edges smooth.

Optimization of Three- and Single-Phase AC HTS Cables Design by Numerical Simulation

This paper presents the results of calculation of ac HTS cables designs optimized by the values of hysteresis and eddy current losses. The superconducting elements of the cables are 2G HTS tapes. The program we developed and used allowed the variation of both the cable shape and its internal structure. There have been considered nonsectioned and sectioned cables having two variants of geometry-the axially symmetrical coaxial and extended rectangular cross-sectional shape. It has been shown that the internal structure optimization allows decreasing of ac losses in several times for both cross-sectional shapes. Due to the compensation of the perpendicular magnetic field component, the characteristics of flat three-phase cables turn out to be close of those with the axially symmetrical cross-sectional shape. In this case, the rectangular cross-sectional shape allows obtaining better mass, dimensional, and mechanical parameters and better cooling conditions of phases. The cables sectioning allows an essential reduction of ac losses. But, the latter is possible only when there is a uniform current distribution over the sections, i.e., at a very exact design calculation.

Theoretical model for optical properties of symmetric trimer nanoholes in a gold film

In this study, optical properties of a symmetric nanohole trimer milled in a gold film are studied using theoretical calculations and numerical simulations. The theoretical model is based on a closed-form relation of the electric and magnetic polarizabilities of a circular nanohole. By modeling each nanohole as a magnetic point-dipole and extending the symmetry-adapted linear combination to the in-plane nanoholes, the mutual effects of the nanoholes on the scattering spectrum are demonstrated. The numerical approach is based on the finite-difference time-domain method, and the numerical results support the theoretical approach. The results indicate that two distinct resonant peaks can be seen in the scattering spectrum of the nanohole trimer, which are due to antibonding and bonding plasmon resonant modes, respectively. The magnetic fields and the corresponding magnetic point-dipoles of the lower nanoholes are in-phase and out-of-phase of the perpendicular and parallel magnetic field components of the incident field, respectively. The upper nanohole at the antibonding resonant wavelength has a phase difference of approximately 30° with the lower nanoholes.

Local Magnetic Suppression of Topological Surface States in Bi2Te3 Nanowires.

Locally induced, magnetic order on the surface of a topological insulator nanowire could enable room-temperature topological quantum devices. Here we report on the realization of selective magnetic control over topological surface states on a single facet of a rectangular Bi2Te3 nanowire via a magnetic insulating Fe3O4 substrate. Low-temperature magnetotransport studies provide evidence for local time-reversal symmetry breaking and for enhanced gapping of the interfacial 1D energy spectrum by perpendicular magnetic-field components, leaving the remaining nanowire facets unaffected. Our results open up great opportunities for development of dissipation-less electronics and spintronics.

Magnetoconductance of a magnetic double barrier in a quantum wire

Magnetotransport measurements of a ballistic quantum wire exposed to two magnetic barriers of opposite polarity in series are reported. We find two types of conductance resonances with quite different characteristic magnetic fields. Numerical simulations show that the first type, characterized by a larger fluctuation period of the magnetoconductance, originates from bound states localized at the magnetic barrier oriented in the same direction with the perpendicular component of the external magnetic field, and the second type of conductance fluctuation can be traced back to states that reside close to the second magnetic barrier with antiparallel alignment. The simulations furthermore show that the confinement mechanism for these states can be understood in terms of spatially varying diamagnetic shifts of the one-dimensional wire modes.

The Utilization of Genetic Algorithm on High Temperature Superconducting Magnet Design

In high temperature superconducting (HTS) magnet design, it well known that the critical current (Ic) is sensitive to the direction of the local magnetic field. The perpendicular magnetic field component to the face of tape have a larger effect on the Icof a HTS tape than the parallel component. Thus in HTS magnet design, the magnetic field distribution is the first considering factor. This work presents a HTS magnet design using genetic algorithm to obtain the object. When the length of the tape is certain, the results show that the process gives the optimal number of the double pancake and the inner radius of the magnet.

Open boundary particle‐in‐cell simulation of dipolarization front propagation

AbstractFirst results are presented from an ongoing open boundary 2½D particle‐in‐cell simulation study of dipolarization front (DF) propagation in Earth's magnetotail. At this stage, this study is focused on the compression, or pileup, region preceding the DF current sheet. We find that the earthward acceleration of the plasma in this region is in general agreement with a recent DF force balance model. A gyrophase bunched reflected ion population at the leading edge of the pileup region is reflected by a normal electric field in the pileup region itself, rather than through an interaction with the current sheet. We discuss plasma wave activity at the leading edge of the pileup region that may be driven by gradients, or by reflected ions, or both; the mode has not been identified. The waves oscillate near but above the ion cyclotron frequency with wavelength several ion inertial lengths. We show that the waves oscillate primarily in the perpendicular magnetic field components, do not propagate along the background magnetic field, are right handed elliptically (close to circularly) polarized, exist in a region of high electron and ion beta, and are stationary in the plasma frame moving earthward. We discuss the possibility that the waves are present in plasma sheet data, but have not, thus far, been discovered.

Comparison of Optimal Configuration of SMES Magnet Wound With $\hbox{MgB}_{2}$ and YBCO Conductors

This paper describes a comparison of an optimal configuration of SMES magnets wound with MgB2 or YBCO conductors. For YBCO SMES, it is well known that a toroidal magnet is an ideal structure from the view point of the influence of the perpendicular component of magnetic field applied to an YBCO tape. We investigated an ideal structure for MgB2 SMES by comparing with the YBCO SMES. Because an MgB2 wire has no anisotropic magnetic property like an YBCO tape, the toroidal structure is unsuitable for MgB2 SMES. Therefore, we proposed a new structure of MgB2 SMES where the magnetic flux leaking between conductors is avoided. An MgB2 SMES of the proposed structure can store approximately 5.6 times higher than that of a single solenoid structure with the same winding volume.

Total AC loss measurements in a six strand Roebel cable carrying an AC current in an AC magnetic field

We measured the total AC loss in a 6/2 (i.e. 6 strands of 2 mm width) Roebel cable by incorporating a transport measurement method for Roebel cable into a total AC loss measurement system. The amplitude and frequency of the external magnetic field and applied transport current, and the field angle θ (the angle between the field and the normal vector to the cable surface) were varied. The results for θ ≤ 60° scale with the perpendicular magnetic field component, and increase with increasing transport current. In the high magnetic field region, the total AC loss values for a current amplitude I ≪ Ic agree with the Brandt model for a 2 mm-wide Roebel strand, not for a thin strip with the Roebel cable width. This shows the advantage of a Roebel cable over equivalent stacks composed of wider conductors. The total AC losses in a parallel magnetic field become more independent of the field amplitude with increasing current amplitude due to the increased dominance of the transport AC losses in the total AC losses. No frequency dependence was observed in the total AC loss data. A maximum entropy model was successfully constructed for the total AC loss results in a perpendicular magnetic field.

Vanishing Meissner effect as a Hallmark of in–Plane Fulde-Ferrell-Larkin-Ovchinnikov Instability in Superconductor–Ferromagnet Layered Systems

We demonstrate that in a wide class of multilayered superconductor-ferromagnet structures (e.g., S/F, S/F/N, and S/F/F') the vanishing Meissner effect signals the appearance of the in-plane Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulated superconducting phase. In contrast to the bulk superconductors the FFLO instability in these systems can emerge at temperatures close to the critical one and is effectively controlled by the S layer thickness and the angle between magnetization vectors in the F/F' bilayers. The predicted FFLO state is revealed through the critical temperature oscillations vs the perpendicular magnetic field component.

Modeling of Two-Dimensional Magnetic Properties Based on One-Dimensional Magnetic Measurements

This paper proposes a modeling method of two-dimensional (2D) magnetic properties based on magnetic energy obtained from several one-dimensional (1D) magnetic properties with different inclination angles from rolling direction. We compare the measurement results of non-oriented electrical steel sheets by 2D and 1D single sheet testers (SSTs) and confirm that almost the same magnetic properties can be obtained from each tester. Based on several 1D magnetic properties measured by the 1D-SST, we evaluate a magnetic energy by using a Fourier series expansion. By differentiating the estimated magnetic energy, we can obtain the perpendicular components of magnetic field with respect to the magnetic flux density which cannot be measured by the 1D-SST. In order to confirm the validity of the proposed method, we compare the estimated 2D magnetic properties with measured ones. Finally, the calculation procedure of the Jacobian matrix is presented and the proposed method is applied to the finite element analysis.

Interplanetary magnetic field orientation and the magnetospheres of close-in exoplanets

The abundance of exoplanets with orbits smaller than that of Mercury most likely implies that there are exoplanets exposed to a quasiparallel stellar-wind magnetic field. Many of the generic features of stellar-wind interaction depend on the existence of a non-zero perpendicular interplanetary magnetic field component. However, for closer orbits the perpendicular component becomes smaller and smaller. The resulting quasiparallel interplanetary magnetic field may imply new types of magnetospheres and interactions not seen in the solar system. We simulate the Venus-like interaction between a supersonic stellar wind and an Earth-sized, unmagnetized terrestrial planet with ionosphere, orbiting a Sun-like star at 0.2 AU. The importance of a quasiparallel stellar-wind interaction is then studied by comparing three simulation runs with different angles between stellar wind direction and interplanetary magnetic field. The plasma simulation code is a hybrid code, representing ions as particles and electrons as a massless, charge-neutralizing adiabatic fluid. Apart from being able to observe generic features of supersonic stellar-wind interaction we observe the following changes and trends when reducing the angle between stellar wind and interplanetary magnetic field 1) that a large part of the bow shock is replaced by an unstable quasiparallel bow shock; 2) weakening magnetic draping and pile-up; 3) the creation of a second, flanking current sheet due to the need for the interplanetary magnetic field lines to connect to almost antiparallel draped field lines; 4) stellar wind reaching deeper into the dayside ionosphere; and 5) a decreasing ionospheric mass loss. The speed of the last two trends seems to accelerate at low angles.

Characterization of Magnetic Field Distribution in a Trailing-Edge Shielded Head by Frequency-Modulated Magnetic Force Microscopy

In this paper, the ac magnetic field distribution of a trailing-edge shielded SPT head were successfully investigated by using a newly developed frequency-modulated magnetic force microscopy (FM-MFM) technique with a hard magnetic MFM tip. The results show sharper magnetic field gradient at the trailing edge than at the leading edge of the main pole. The perpendicular component of the magnetic field of the main pole region is opposite to that of the trailing shield/return pole region. As the write current increases, the saturation of magnetic field in the main pole region occurs from the trailing edge first. With increasing write current, the return field of the trailing shield edge increases significantly as well, which may cause return field-induced partial erasure. The double-peak feature of the distribution of ac magnetic field generated from the head only depends on the tip-sample distance and does not depend on the input write current. The FM-MFM technique used in this work was proved to be applicable in the imaging of the ac magnetic field of a recording head with high spatial resolution.

Estimation of magnetization loss at angular magnetic field using perpendicular magnetization loss in striated and transposed YBCO coated conductor

The magnetization loss in a perpendicular external magnetic field is main AC loss of YBCO coated conductor for AC power applications. One of solutions for decreasing the magnetization loss is to make striations on it and to transpose the striated coated conductors. We measured the magnetization losses of several samples made by striated and transposed YBCO coated conductors in external magnetic field with an inclined angle for wide face of YBCO coated conductor. We compared the measured magnetization loss at an arbitrary direction in the magnetic field with those measured in a perpendicular magnetic field at the same value of perpendicular component of the external magnetic field. The results agree well with each other in all samples. This means that the magnetization loss in any directional applied magnetic field can be estimated by using only the perpendicular loss data.

Experiment VARIANT – first results from Wave Probe instrument

The international experiment VARIANT was carried out onboard Ukrainian remote sensing satellite SICH-1M launched 2004, December 24. In spite of other than planned satellite orbit and onboard systems failure about 11 telemetric files from VARIANT payload were obtained. Due to episodic and random payload switching the main goal of VARIANT experiment - study of field aligned currents and monitoring of electromagnetic state of the ionosphere – was not possible to realize. However the data analysis from VARIANT instrumentation allowed us to obtain for the first time a reliable confirmation of proper operation in ionospheric plasma of a new device developed for wave activity study – Wave Probe, which consists of compact combination of Split Langmuir Probe working at floating potential and search-coil magnetic field sensor. Such a probe can simultaneously measure variations of one component of spatial current density and a perpendicular component of magnetic field with a spectral sensitivity threshold up to 0.1 pA/(cm 2 Hz 1/2) and 0.03 pT/Hz 1/2, respectively.

New shape of superconducting coil with improved critical current – design and FEM analysis results

The novel superconducting HTS coil designed for Superconducting Magnetic Energy Storage (SMES) is the aim of the paper. Novelity lies in the shape of the coil that minimises perpendicular component of the flux density of HTS wire. In this paper authors try to find the shape of the coil where perpendicular component of magnetic field is as close as possible to zero. Proposed solution has the helical shape of coil turns and the special shape of the magnetic core (magnetic core with air gap is needed for increasing stored energy). Helical turns are put on toroidal former and then magnetic core on it. Each turn has the same shape, length and is put in the same magnetic flux. Near-uniform distribution of magnetic flux is the result of the shape of winding and also non-uniform shape (or non-concentric) of magnetic core that has multiple radial air gaps. It produces magnetic field distribution in magnetic core shaped coaxially to winding and distribution of stored magnetic energy uniformly on magnetic core circumference. Magnetic energy is stored in air gaps and proposed shape of core is the best solution of core but its fabrication produces technological difficulties in core manufacturing.

Magneto-optic imaging: Normal and parallel field components of in-plane magnetized samples

Magneto-optical (MO) imaging has become a powerful tool for determining magnetic properties of materials by detecting the stray magnetic fields. The technique consists in measuring the Faraday rotation, θ F , in the light polarization plane when light travels through a transparent sensitive garnet (ferrite garnet film, FGF) placed in close contact to the sample. For in-plane magnetized samples, the MO image is not trivially related to the sample magnetization, and to contribute to this understanding we have imaged commercial audio tapes in which computer-generated functions were recorded. We present MO images of periodically in-plane magnetized tapes with square, sawtooth, triangular and sinusoidal waveforms, for which we analytically calculate the perpendicular and parallel stray magnetic field components generated by the tape. As a first approach we correlate the measured light intensity with the perpendicular magnetic field component at the FGF, and we show that it can be approximated to the gradient of the sample magnetization. A more detailed calculation, taking into account the effect of both field components in the Faraday rotation, is presented and satisfactorily compared with the obtained MO images. The presence of magnetic domains in the garnet is shown to be related to the change in sign of the parallel component of the stray magnetic field, which can be approximated to the second derivative of the sample magnetization.

Design and Test of High-<tex>$T_C$</tex>Superconducting Coils for a Three-Phase 10.5 kV/1.5 kA Fault Current Limiter

The design and test of High Temperature Superconducting (HTS) coils for a three-phase 10.5 kV/1.5 kA HTS fault current limiter (FCL) are described. It is well known that the critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of HTS materials is very sensitive to the orientation of fields. In the design of HTS coils, the value of the perpendicular component of magnetic field (B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">perp</sub> ) should be reduced, and the coils should be wound and jointed easily. In order to enlarge the current carrying capacity of the coil, the double pancakes in the coils were connected in parallel. Based on the field distribution in the coil and the current distribution in each double pancake, the design of the coil was optimized. Three coils wound with Bi-2223/Ag tape have been developed and tested in liquid nitrogen

A Study on Mitigation Method of Perpendicular Magnetic Field in HTS Superconducting Coils for Power Transformer

Methods to mitigate a perpendicular magnetic field component on the surface of a high temperature superconducting (HTS) tape in HTS coils by arranging low current density (LCD) coils in the edges were studied analytically. Four types of winding arrangement with and without the LCD coils at both edges of the superconducting winding, which are used to model a three-phase 40 MVA HTS transformer, were proposed. The results of magnetic field analysis in the proposed winding arrangements reveal that (1) the maximum perpendicular magnetic field (B/sub /spl perp/max/) on the surface of the HTS tape is influenced markedly by the LCD coils arrangements and that (2) the winding arrangement which is LCD coils installed in both edges of top and bottom in the LV and the HV winding is very effective in reducing the B/sub /spl perp/max/ in both edges of top and bottom.

Numerical analysis of AC losses in YBCO coated conductor in external magnetic field

For electric power applications of YBCO coated conductors, the reduction and estimation of AC losses are important issues. This paper reports numerical analysis of electromagnetic phenomena in YBCO coated conductor with particular emphasis on AC loss characteristics. FEM analysis of electromagnetic fields was carried out with strongly nonlinear E– J characteristics of superconductor, and the dependence of AC losses on angle of external magnetic field was investigated. The results indicate that the AC losses depend almost only on the perpendicular component of external magnetic field, while at a higher magnetic field the AC losses also slightly depend on the parallel component.