“神龙二号”气体火花开关中绝缘结构的电场分析与优化

气体火花开关作为重要部件被大量地应用于直线感应加速器和Z箍缩等大型脉冲功率装置中。绝缘结构设计不合理会使得气体火花开关中出现局部电场畸变和电荷积聚等现象。在高电压脉冲下长时间或高频次运行时，火花开关中的绝缘子会发生沿面闪络现象，直接影响到脉冲功率装置的正常运行。鉴于此，对气体火花开关中的绝缘结构进行了有限元电场分析，用表面电荷的积聚定性解释了沿面闪络发生的原因。通过对绝缘子的几何结构和电极尺寸的优化设计，有效降低了绝缘子表面和电极表面的电场强度，其中阳极三结合点场强从9.4 kV/mm降至1.5 kV/mm，阴极三结合点场强从2.95 kV/mm降至0.98 kV/mm，绝缘子表面最高场强从10.8 kV/mm降至4.95 kV/mm。优化后的绝缘结构电场分布较为合理，降低了由于表面电荷的积聚而引发沿面闪络的概率。

Electric field analysis and optimization of the insulation system in gas-filled spark gap switch of Dragon-Ⅱ accelerator

In linear induction accelerator, Z-pinch and other large pulsed power devices, the gas-filled spark gap switches as key components are widely used. Unreasonable insulation system may bring excessively high partial electric field and accumulated charges to the gas-filled spark gap switch. The surface flashover would occur while the gas-filled spark gap switches are working under long time or high frequency high voltage pulse. The surface flashover will directly affect the pulsed power devices. Hence, we discussed the mechanism of accumulated charge influence on surface flashover by finite-element electric-field analysis of gas-filled spark gap switch insulation system. The surface electric field strength of insulator and electrodes were reduced by optimizing the structure of insulator and shapes of electrode surface. The results show that: the electric field strength in anode triple junction was decreased from 9.4 kV/mm to 1.5 kV/mm, the electric field strength in cathode triple junction was decreased from 2.95 kV/mm to 0.98 kV/mm, the maximum electric field strength in insulator surface was decreased from 10.8 kV/mm to 4.95 kV/mm. The electric field distribution of optimized insulation system was more reasonable than that of original system, and the probability of surface flashover resulted by accumulated charges would be reduced.