高功率微波沿面闪络击穿机制粒子模拟

针对高功率微波介质沿面闪络击穿物理过程，首先建立了理论模型，包括：动力学方程、粒子模拟算法、二次电子发射, 以及电子与气体分子蒙特卡罗碰撞模型、电子碰撞介质表面退吸附气体分子机制；其次，基于理论模型，编制了1D3V PIC-MCC程序，分别针对真空二次电子倍增、高气压体电离击穿和低气压面电离击穿过程，运用该程序仔细研究了电子和离子随时间演化关系、电子运动轨迹、电子及离子密度分布、空间电荷场时空分布、电子平均能量、碰撞电子平均能量、碰撞电子数目随时间演化关系、电子能量分布函数、平均二次电子发射率以及能量转换关系。研究结果表明：真空二次电子倍增引发的介质表面沉积功率只能达到入射微波功率1%左右的水平，不足以击穿；气体碰撞电离主导的高气压体电离击穿，是由低能电子（eV量级）数目指数增长到一定程度导致的，形成位置远离介质表面，形成时间为s量级；低气压下的介质沿面闪络击穿，是在二次电子倍增和气体碰撞电离共同作用下，由于数目持续增长的高能电子（keV量级）碰撞介质沿面导致沉积功率激增而引发的，形成位置贴近介质沿面，形成时间在ns量级。

PIC simulation of mechanism of high power microwave flashover and breakdown on dielectric surface

For investigating the mechanism of high power microwave flashover and breakdown on dielectric surface, the theoretical modeling is put forward, including dynamic equations, particle-in-cell method, secondary emission and Monte-Carlo collision between electrons and gas atoms. Based on the theoretical model, the 1D3V PIC-MCC code is programmed. By using this code, we numerically study vacuum multipactor discharge, volume breakdown under high-pressure gas and surface breakdown under low-pressure gas course, including the number of electrons and ions, electron trajectories, electron and ion density distributions, the time and space distribution of space charge field, the average electron energy, the average energy of impact electrons, the number of impact electrons, electron energy distribution functions, average secondary emission ratio and energy balance. The numerical results are concluded as follows: vacuum multipactor could not cause breakdown for low deposited power (about 1% microwave power); volume breakdown is caused by high-level number of electrons with low energy, the breakdown position is far from dielectric surface, and the forming time is at the level of microseconds; flashover and breakdown on dielectric surface are caused by the continuous increase of deposited power resulting from many high-energy electrons, the breakdown position is near to dielectric surface, and the forming time is at the level of nanoseconds.