真空高压二极管的绝缘结构分析

Analysis of Dielectric Structure in High Voltage Vacuum Diode

为提高真空高压二极管中绝缘子的耐压能力,利用静电场有限元模拟、电磁PIC模拟及传统理论计算的方法,分析了计及实际环境中绝缘子与电极之间微小间隙存在时绝缘子几何形状、绝缘材料与电极接触方式、电极结构、特别是导引磁场及回流电子对绝缘子耐压能力的影响。研究表明,抑制阴极三结点处场增强效应、尽量避免电子轰击绝缘子表面以控制解吸附气体量、适当的绝缘表面处理有利于提高绝缘子耐压能力,可作为设计真空高压二极管绝缘子的基本原则,并给出了一些具体的建议。

The breakdown voltage on the vacuum side of the insulator is generally much lower than the bulk breakdown voltage, but supporting very high electron fields in a vacuum environment is essential for compact pulse power system. In order to improve the HV hold off capability of insulator in high voltage vacuum diode, considering the presence of small voids between the insulator and electrode in reality, several factors such as the insulator geometry, material, the way of attachment to electrodes , the configuration of electrodes ,especially in the absence of the applied guide magnetic field and the reflux of electrons, are discussed of their influence on the HV hold off capability of insulator by use of the finite element method for electrostatic field analysis, Electromagnetic PIC simulation and traditional theoretical calculation. It can be found that restraining the equip potential concentrating effect at the cathode triple junction so as to restrain the field electron emission, trying one＇s best to prevent the electrons from impacting the insulator surface so as to control the quantity of the desorbed surface gas, and appropriate surface treatment, are helpful to improve the hold off capability of insulator . so they can be used as the principia in designing the insulator of high voltage vacuum diode, some concretely method, such as adopting the positive forty-five degree frustum, selecting the dielectric with lower permittivity and lower outgas rate, using the shielding ring, designing the electric field and the guiding magnetic field reasonable in the absence of reflux electron, the reasonable surface treatment on the insulator, are summarized here.