共查询到20条相似文献,搜索用时 473 毫秒
1.
2.
3.
4.
An electron-beam system for use in microfabrication is described. Postlens deflection coils have been used with dynamic correction of the final lens to obtain an electron optical resolving power of about 10 000 lines over a 1 × 1 cm field. 相似文献
5.
基于空间向量积分法建立了共轴涡旋结构载流线圈的解析模型,计算了磁场及磁力,并对特殊取值下的磁场空间分布进行了数值分析和讨论。基于仿真结果,提出线圈密绕情况下的近似模型并进行了相应的误差分析。结果表明,所提模型可有效地直接对磁场分布进行近似,但需对受力近似进行一定的补偿。 相似文献
6.
A versatile exposure system which can be used to investigate the effects of a 60-Hz alternating magnetic field or traveling magnetic field on small laboratory animals is described. Special attention was given to the design of the electric circuit to simplify the supply requirements and to keep the overall current to a minimum. A magnetic field having a flux density up to 30 mT (300 G) can be generated, and a traveling magnetic field is obtained by reconnecting the coils to a three-phase supply. The total magnetic field due to the currents in the three coils used in the exposure system is analyzed. A computer program was written to evaluate the magnetic field in the region where the animals are located. The difference observed between measured and computed values is attributed to the representation of the multiturn, multilayer coils by equivalent single-turn coils 相似文献
7.
8.
《Electron Devices, IEEE Transactions on》1969,16(9):798-803
Bobbin-type air core coils have been designed and experimentally evaluated for astigmatic properties in line scan operation over deflection angles of ± 20°. The approximate design technique is successful in specifying the proper operating focal distance when this is comparable to the coil length. Line fields in excess of 20 000 spot diameters have been measured using a 10 kV beam having a 5 × 10-3radian convergence half-angle. 相似文献
9.
The finite-difference time-domain (FDTD) method is combined with the method of moments (MoM) to compute the electromagnetic fields of shielded radio-frequency (RF) coils loaded with an anatomically accurate model of a human head for high-frequency magnetic resonance imaging (MRI) applications. The combined method can predict both the specific energy absorption rate (SAR) and the magnetic field (known as the B1 field) excited by any RF coils. Results for SAR and B1 field distribution, excited by shielded and end-capped birdcage coils, are calculated at 64, 128, 171, and 256 MHz. The results show that the value of SAR increases when the frequency of the B1 field increases and the B1 field exhibits a strong inhomogeneity at high frequencies 相似文献
10.
Analytical and experimental investigation on the magnetic field and torque of a permanent magnet spherical actuator 总被引:2,自引:0,他引:2
Liang Yan I-Ming Chen Guilin Yang Kok-Meng Lee 《Mechatronics, IEEE/ASME Transactions on》2006,11(4):409-419
This paper presents the torque model of a ball-joint-like three-degree-of-freedom (3-DOF) permanent magnet (PM) spherical actuator. This actuator features a ball-shaped rotor with multiple PM poles and a spherical stator with circumferential air-core coils. An analytical expression of the magnetic field of the rotor is obtained based on Laplace's equation. Based on this expression and properties of air-core stator coils, Lorentz force law is employed for the study of the relationship between the rotor torque and coil input currents. By using linear superposition, the expression of the actuator torque in terms of current input to the stator coils can be obtained in a matrix form. The linear expression of the actuator torque will facilitate real-time motion control of the actuator as a servo system. Experimental works are carried out to measure the actual magnetic field distribution of the PM rotor in three-dimensional (3-D) space as well as to measure the actual 3-D motor torque generated by the actuator coils. The measurement results were coincident with analytical study on the rotor magnetic field distribution and actuator torque expressions. The linearity and superposition of the actuator torque were also verified through the experiments. 相似文献
11.
The computational methods of deflection fields in magnetic yokes with wedged coil-sections and electrostatic deflectors with
planar electrodes are discussed. The magnetic yokes with wedged coil-sections can be combined into various shapes of magnetic
deflectors, which may offer a variety of choices for adjusting the deflection field distributions to reduce the deflection
aberrations more effectively. An advantage of the planar electrostatic deflectors is the simplicity in structure, which might
allow the deflectors to be used in the deflection array of multi-electron beam lithography systems. Based on the methods described
in this paper two computer programs have been developed. As examples, the deflection field distribution of some typical deflectors
have been computed. 相似文献
12.
13.
Anashin V. Bulygin A. Labutsky S. Mejidzade V. Mikhailov S. Pupkov Y. Rouvinsky E. Sukhina B. Kalbreier W. Kouba G. Schirm K.M. Weisse E. Konstantinov Y. Kosjakin M. Peregud V. 《Applied Superconductivity, IEEE Transactions on》2002,12(1):120-124
Two injection transfer lines, each about 2.8 km long, with 51 and 107 degree horizontal deflection, are being built to transfer protons at 450 GeV from the Super Proton Synchrotron (SPS) to the Large Hadron Collider (LHC). A total of 360 dipole magnets are required; they have been produced in the framework of the contribution of the Russian Federation to the construction of the LHC. The classical dipoles, built from laminated steel cores and copper coils, have a core length of 6.3 m, 25 mm gap height and a nominal field of 1.81 T at a current of 5270 A. The magnet design was made in collaboration between CERN and BINP. An unusual design has been chosen for the coils to cope with the limited voltage from the available power supplies. All magnets in each of the two lines will be powered in series. The coil is composed of overlapping, but electrically insulated, half coils of 3 1/2 turns each. Thus, the power connections for IN and OUT are placed on opposite magnet ends. Short copper braids are used to connect all upper or lower half coils in series and the whole string can be powered without power consuming cable links running alongside the magnets. Precautions are taken to avoid transmission line effects and hazards from differences in voltage between upper and lower half coil. Advantages and drawbacks of this concept are discussed as well as results of the acceptance test including mechanical, electrical and magnetic field measurements. Fabrication and measurement of the magnets at BINP, with the half core production subcontracted to EFREMOV, have been finished in June 2001. 相似文献
14.
大通量冷原子源是实现高精度冷原子干涉仪的关键技术之一。为获得大通量冷原子源,通常采用二维磁光阱(2D-MOT)和三维磁光阱(3D-MOT)的级联结构,其中2D-MOT的磁场分布是影响其性能的重要因素。通过数学建模及有限元分析,对2D-MOT中不同构造(长方形、跑道形、马鞍形)的反亥姆霍兹线圈进行数值计算,分析了不同构造线圈的磁场分布及因在制造与装配过程中产生的偏心、线圈不对称、平行度及内径不对称误差造成的磁场零点漂移和磁场梯度变化。分析结果表明,在偏心误差C1.14 mm,线圈不对称误差I0.016 A,平行度误差1.02时,马鞍形线圈产生的磁场梯度更有利于制备大通量冷原子源。该结果为冷原子干涉仪2D-MOT的磁场系统设计和加工提供了理论指导。 相似文献
15.
16.
根据Raman and Nath理论,光在声场中传播可认为是在多层薄光栅中传播,而薄光栅的参数则由光栅平面内的声场分布决定。本文通过圆对称聚焦换能器在焦平面附近的声场分布,得到光束的偏转角与换能器焦点声压的关系。通过测量光束偏转距离得到换能器焦点声压。虽然本文的声压与偏转角的关系是基于理想超声聚焦换能器的线性理论,但通过激光检测声压与光纤水听器测量的结果,表明该方法可用于检测较高的焦点声压检测。 相似文献
17.
研究了线圈间距、匝数、个数以及不锈钢套筒对脉冲磁体产生磁场的影响规律。在储能电容和电压不变的前提下,研究结果表明:增加线圈间距会导致磁感应强度降低,磁力线包络增大,但总电流达到峰值时刻减小;增加线圈匝数,峰值电流明显减小,会降低磁感应强度,但有利于抑制磁力线包络;增加并联线圈个数,有利于产生较长的均匀区,但是在供能一定的条件下,磁场强度有所降低,同时总电流达到峰值时刻减小。总体来看,在一定均匀区长度的设计要求下,减少单个线圈匝数,增加并联线圈个数,能够得到磁感应强度更大、均匀性更好的磁场,但要考虑线圈承载电流的能力。另外,不对称的阴阳极金属结构会导致磁场不对称分布,且磁感应强度达到峰值时刻要晚于总电流达到峰值的时刻。 相似文献
18.
19.
In a wireless power transfer (WPT) system, the transfer performance is related to the mutual inductance between coils. However, the mutual inductance decreases with the increase of transfer distance. In this work, the relationship between the output voltage and the mutual inductance for WPT systems with air core and with ferrite core are analyzed. In order to improve the mutual inductance, a novel configuration of receiving resonator with a strong magnetic coupling is proposed. The mutual inductance and magnetic field distribution for coils with a cylindrical core and with the novel configuration are compared. Experiments are carried out for validation. The results indicate that the proposed WPT system is superior to the system with the cylindrical ferrite core in increasing the output voltage and power transfer efficiency. 相似文献
20.
I. P. Korshunov E. N. Korshunova A. D. Oleinikov A. D. Shatrov 《Journal of Communications Technology and Electronics》2009,54(10):1146-1155
The frequency-selective properties of small screw helical coils are investigated. It is shown that, in a frequency band of
2–4 GHz, such coils have two resonances. The scattering patterns of helical coils are measured in the E and H planes. It is found that, at the zeroth-order resonance, a coil scatters a circularly polarized field with the maximum in
the plane perpendicular to its longitudinal axis and that, at the frequency of the first resonance, the maximum of the scattered
field is oriented along the longitudinal axis of the coil. 相似文献