磁悬浮微进给机构电磁场研究

针对微电子行业IC芯片制造设备如光刻机而设计了磁悬浮微进给机构,并对它进行了电磁场耦合分析及解耦控制,准确综合地研究磁悬浮系统。在不计漏磁的简单磁路、磁力计算基础上,采用有限元分析软件ANSYS对电磁场进行有限元分析,得到考虑漏磁的磁场分布及准确的磁力计算结果,从而确定电流及气隙大小等悬浮控制参数,为控制设计与试验提供了参考。     

Experimental evaluation of the total shielding current in a bulkhigh-Tc superconductor [YBaCuO]

Total shielding currents of a melt processed bulk high-Tc superconductor (HTS) are evaluated from the measured voltage of a Rogowski coil when a permanent magnet is moved towards the HTS. The total shielding current and the levitation force between the magnet and the HTS show rapid growth and decay depending on the speed of the magnet. The dynamic levitation force and the magnetic relaxation are discussed from the experimental results     

Optimization of Permanent Magnet Guideway for HTS Maglev Vehicle With Numerical Methods

Because of the disadvantages of the existing permanent magnetic guideway (PMG) such as low efficiency, a Halbach PMG is proposed to improve the levitation performance of high-temperature superconducting (HTS) magnetic levitation (maglev) vehicle. Magnetic induction of the Halbach PMG is calculated by an analytical method. The screening current density distribution in the superconductor is solved with the flux flow-creep model by the finite-element method, and then the levitation force between the HTS bulk and PMG is calculated by the Lorentz force formula. According to the characteristic of the maglev vehicle, an optimality criterion is proposed to evaluate the levitation performance for the HTS maglev vehicle.      

Numerical evaluation of levitation force of HTSC flywheel

Levitation force between permanent magnets and high-T_c superconductors (HTSC's) is evaluated numerically based on the critical state model. The bulk HTSC is approximated to a thin plate multilayer model from its anisotropic structure. The thin plate eddy current code with the finite element method is applied to the analysis of the HTSC flywheel, where ring magnets and the HTSC are arranged in triple concentric circles. The size and the combination of the magnets are examined to obtain the large levitation force. It is shown that the levitation force of the HTSC flywheel depends strongly on the magnetic field configuration     

Scattering of the field of a ring current by a perfectly conducting disk

Asymptotic formulas are obtained for scattering patterns of the field produced by ring magnetic and electric currents with a harmonic azimuthal dependence that are located coaxially over a perfectly conducting disk. The calculation is performed according to the obtained formulas for the cases of the in-phase current and the current with a single azimuthal-angle variation. The dependence of the front-to-back ratio on the disk radius is investigated. Numerical data are compared to the results obtained with the help of the integral equation method.     

Measurement of AC magnetic field distribution using magneticresonance imaging

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

Coupled-mode theory for magneto-optical fiber Bragg grating under non-uniform magnetic field

According to the perturbation theory, the coupled-mode equations for guided optical waves in the magneto-optical fiber Bragg gratings (MFBGs) under non-uniform magnetic field are derived. The equivalent relation between the magnetically-induced non-uniform fiber Bragg grating (MnFBG) and the corresponding non-magnetic chirped grating is expressed and verified by the piecewise-uniform MFBG model under linear magnetic field. On the basis of the equivalent relation, the MnFBGs can be effectively investigated by means of simulations. The characteristics of the MnFBGs under three typical magnetic field distributions with application to optical pulse compression are simulated, and the minimal pulse width can be achieved for the same magneto-optical coupling parameter of 2.2 × 10³ m⁻¹.     

Electromagnetic field near rail guns

The field in the neighborhood of an electromagnetic rail gun is computed for the case of constant current. The analysis centers on the Westinghouse EMACK launcher in which two rails of 2-m length carry a peak current of 2.1 MA, while a peak power of over 10 GW is delivered to the rails. Expressions are derived for electric field strength and magnetic flux density as functions of gun parameters. These formulas can be used to compute the electromagnetic pulse produced by a rail gun of any given characteristics     

Disk generator

The use of the disk generator as a practical device for power generation is discussed and compared to a linear device in terms of maximum allowable electric fields, magnetic field utilization, and surface-to-volume ratio. The swirl induced by the azimuthal force acting on the radial current is found to be of prime importance for the generator's performance. For certain values of the inlet swirl opposing the azimuthal Lorentz force, the output current becomes a conductive current as in a Faraday generator, and this results in increased efficiency for given Hall coefficients and loading. Examples ad design concepts are discussed.     

Effect of a strong axial magnetic field in the plasma recombinationand extreme ultraviolet emission from a highly-ionized capillarydischarge

The effect of an externally applied 70-100-kG axial magnetic field in the temporal evolution of the extreme ultraviolet emission from a 500-μm-diameter highly ionized LiH capillary discharge is studied. In the absence of external magnetic confinement, strong emission from ionic transitions excited by collisional recombinations is observed at the end of the current pulse. The externally applied magnetic field is observed to reduce the intensity of the recombination lines by decreasing the rate of plasma cooling by electron heat conduction to the capillary walls. In contrast, the self-generated magnetic field of the discharge aids to the generation of an initially hot plasma, and allows rapid conduction cooling at the end of the current pulse. The results are discussed in relation to a proposed capillary-discharge-excited extreme ultraviolet recombination laser scheme     

Ku波段低磁场返波管振荡器的模拟与实验

为了实现高功率微波(HPM)系统小型化,结合传统低磁场相对论返波管振荡器(RBWO)的设计理论,设计一个Ku波段较低磁场的相对论返波振荡器。分析束压、束流、引导磁场等对输出微波的影响,并采用粒子模拟软件(PIC)优化结构。当轴向引导磁场为0.4 T,电子束束压和束流分别为600 k V和7 k A时,得到频率为13.08 GHz,功率为1.0 GW的微波输出。在强流电子束加速器平台上开展实验验证模拟结果:外加磁场0.4 T时,得到平均功率为850 MW、频率13.05 GHz、脉宽24 ns的微波输出。该实验结果为实现较低磁场GW级微波输出打下了良好的基础。     

低磁场S波段相对论返波振荡器模拟与实验

为实现高功率微波(HPM)系统的小型化,设计一个S波段较低磁场相对论返波管(RBWO)振荡器.针对低磁场特点,分析慢波结构、引导磁场、束压、束流等对输出微波的影响,通过模拟软件(PIC)优化结构.以此设计引导磁场为0.24 T,电子束束压为725 kV,束流为6 kA,频率为3.53 GHz,输出微波功率为1.22 G...     

16th International Conference on Magnet Technology (MT-16 1999)

The following topics were discussed: the superconducting magnets for the Large Hadron Collider; superconducting magnets for the Relativistic Heavy Ion Collider; undulators; the RIKEN cyclotron; HERA magnets; high field dipole magnets; detector magnets; the CMS detector; the ATLAS detector; high field solenoid magnets; fusion magnets; magnet electrodynamics; magnetic resonance; energy storage; superconducting power transformers; permanent magnets; magnetic levitation; low temperature superconductors; cable in conduit superconductors; high temperature superconductors; current leads and cryogenics     

Integrated semiconductor magnetic field sensors

A magnetic field sensor is an entrance transducer that converts a magnetic field into an electronic signal. Semiconductor magnetic field sensors exploit the galvanomagnetic effects due to the Lorentz force on charge carriers. Integrated semiconductor, notably silicon, magnetic field sensors, are manufactured using integrated circuit technologies. Integrated sensors are being increasingly developed for a variety of applications in view of the advantage offered by the integration of the magnetic field sensitive element together with support and signal processing circuitry on the same semiconductor chip. The ultimate goal is to develop a broad range of inexpensive batch-fabricated high-performance sensors interfaced with the rapidly proliferating microprocessor. This review aims at the recent progress in integrated silicon magnetic devices such as integrated Hall plates, magnetic field-effect transistors, vertical and lateral bipolar magnetotransistors, magnetodiodes, and current-domain magnetometers. The current development of integrated magnetic field sensors based on III-V semiconductors is described as well. Bulk Hall-effect devices are also reviewed and serve to define terms of performance reference. Magnetic device modeling and the incorporation of magnetic devices into an integrated circuit offering in situ amplification and compensation of offset and temperature effects are further topics of this paper. Silicon will continue to be aggressively exploited in a variety of magnetic (and other) sensor applications, complementary to its traditional role as integrated circuit material.     

新型非接触供电的磁悬浮灯饰的研制

提出一种非接触供电与电磁悬浮技术相结合的实现方案。非接触供电利用电源测的线圈产生的交变磁场耦合到负载侧的线圈,进而将电能传递给负载,而电磁悬浮技术是利用电磁力来控制物体悬浮的空间位置。将两项技术相结合,研制了一种无线供电磁悬浮灯饰,具有安全便利、美观别致、照明效果好等特点,具有良好的市场前景。     

On the transient radiation of energy from simple currentdistributions and linear antennas

Smith (1998) examined the radiation from two simple filamentary current distributions: traveling-wave and uniform. The radiated or far-zone electric field was computed for an excitation that was a Gaussian pulse in time. Two interpretations for the origin of the radiation were presented, based on the far-field results. The present article continues this investigation; however, the emphasis is on an examination of the near field and the related transport of energy away from the current filament. We examine traveling-wave and standing-wave current distributions, because these distributions are frequently used to model practical antennas. Exact analytical expressions are presented for the electric and magnetic fields of the assumed, filamentary current distributions when the excitation is a general function of time. For the filamentary distributions, the current and charge are confined to a line (a line source). There is no radius associated with the filament. The expressions for the fields apply in both the near and far zones, and are used to determine the Poynting vector. For an excitation that is a Gaussian pulse in time, exact analytical expressions are obtained for the energy leaving the filament per unit time per unit length, the total energy leaving the filament per unit length, and the total energy radiated. Graphical results based on these expressions are used to study the energy transport from the filamentary current distributions. The results for the standing-wave current distribution are compared with those from an accurate analysis of a pulse-excited, cylindrical monopole antenna, performed using the FDTD method     

On the electromagnetic field of a rectangular patch of uniform andlinear distributions of current in the source region

Exact analytical expressions for the magnetic vector potential and the electric and magnetic fields of a rectangular patch of uniform and linear distributions of electric current in an unbounded homogeneous medium have been given by the authors in a previous paper (see ibid., vol.37, p.1503-9, December 1989). In this paper, these expressions are utilized to investigate the nature of the electromagnetic field of such current distributions in the source region. Specifically, the singular parts and points of singularity of the various functions involved in the analytical expressions, as well as those of the field components of both current distributions, are obtained and tabulated     

电磁搅拌辅助钛合金激光沉积修复的电磁场模拟与验证

利用自行研制的电磁搅拌装置辅助钛合金激光沉积修复,通过有限元软件ANSYS进行数值模拟,并与试验相结合,研究了钛合金激光熔池内磁-电-力的相互作用关系。结果表明,在旋转磁场的作用下,激光熔池内的液体表面磁感应强度与激励电流成正比,与频率成反比;激光熔池受到径向力和切向力的作用,但是前者较小,可以忽略不计,液体横截面上电磁力密度最大值与激励电流成正比。在旋转磁场的作用下激光沉积修复件表面两侧凸起且修复层内部组织/片层长径比减小。     

透射电子显微镜原位磁场双倾样品杆的研制

本文简述了透射电镜磁场双倾样品杆的设计方案,展示了Philips/FEI透射电镜磁场双倾样品杆的研制成果.利用该样品杆可以产生100 Oe的连续磁场,也可以产生140 Oe以上的瞬间磁场.通过“U”型磁组件和样品杯的巧妙设计,尽可能的减小了电子束在横向磁场中的偏移量.     

On the modal expansion of resonator field in the source region

Two field expansions for the electromagnetic field radiated by electric and magnetic currents in a cavity resonator are presented. The first utilizes the cavity resonant modes only, while the other utilizes, in addition, the irrotational modes. The first expansion is shown to be more suitable if the exciting currents have volume distributions. On the other hand, the second expansion is more suitable if the resonator contains surface or filamentary current distributions. Typical examples are given to demonstrate the convergence behavior of the two expansions near and within the source region