基于流体模型和非平衡态电子能量分布函数的高功率微波气体击穿研究

High power microwave breakdown in gas using the fluid model with non-equilibrium electron energy distribution function

用流体模型研究高功率微波气体击穿时,电子能量分布函数常被假设为麦克斯韦分布形式,此假设可能将给模拟结果带来较大的误差.通过求解玻尔兹曼方程,得到非平衡状态下的电子能量分布函数.分别将上述两类分布函数引入到流体模型中,对氩气击穿进行了数值模拟.结果表明,基于非平衡分布函数得到的击穿时间与粒子模拟结果符合得很好,而当平均电子能量较低时,麦克斯韦分布函数的高能尾部导致了较短的击穿时间.最后,采用非平衡分布函数计算了不同压强下的氩气击穿阈值,发现其与实验结果基本符合.

The electron energy distribution function （EEDF） is usually assumed to be of the Maxwellian distribution in the fluid model in the simulation of high power microwave breakdown in gas. However, this assumption may lead to some large errors in the simulations. In this paper we compute the non-equilibrium EEDF via solving the Boltzmann equation directly, and incorporate it into the fluid model for argon breakdown. Numerical simulations show that the breakdown time obtained by the fluid model with the non-equilibrium EEDF accords well with the Particle-in-cell-Monte Carlo collision simulation result, while the Maxwellian EEDF has higher energy tail and results in faster breakdown time at low mean electron energy. Based on the non-equilibrium EEDF, the dependence of the breakdown threshold on the pressure predicted by the fluid model accord well with the argon breakdown experimental result.