高功率微波介质窗气体侧击穿特性的粒子-蒙特卡罗碰撞模拟  

Particle-in-cell-Monte Carlo collision simulation study on gas side breakdown characteristics of high-power microwave dielectric window

作　　者：舒盼盼 赵朋程[2] Shu Pan-Pan;Zhao Peng-Cheng(School of Science,Xi’an University of Technology,Xi’an 710054,China;School of Physics,Xidian University,Xi’an 710071,China)

机构地区：[1]西安理工大学理学院,西安710054 [2]西安电子科技大学物理学院,西安710071

出　　处：《物理学报》2024年第23期157-166,共10页Acta Physica Sinica

基　　金：陕西省自然科学基础研究计划(批准号:2023-JC-YB-512,2023-JC-YB-042)资助的课题.

摘　　要：在高功率微波介质窗外表面周围,气体击穿是限制功率容量提升的主要因素之一,因此进行相应的模拟研究具有重要的意义.本文通过粒子-蒙特卡罗碰撞模型对介质窗气体侧击穿特性进行了模拟研究.将宏粒子合并方法引入该模型,大大减少了跟踪的宏粒子数量,以至于能够对整个击穿过程进行模拟与分析.结果表明,在宏粒子权重为变量下,击穿的时空演化特性与宏粒子权重为常数下的结果符合得很好.由于次级电子发射产额远小于1,所以气体电离是介质窗气体侧击穿的主导机理.电子电离和扩散导致等离子体的密度和厚度随着时间显著增加.电子密度的峰值未出现在介质表面处而是在距离介质表面100—150μm的位置.这是因为大量的电子沉积在介质表面上,伴随产生的自组织法向电场驱使电子远离介质表面.由于本文关注的背景气体压强高于最大电离率对应的临界压强(约为1.33×10^(3)Pa),所以电离率随着压强的增加而单调减小,并导致击穿发展得更加缓慢.通过比较击穿时间的模拟值与实验数据,证实了粒子-蒙特卡罗碰撞模型的准确性.Gas breakdown is one of the key factors limiting the increase of power capacity of the outer surface of highpower microwave dielectric window.It is of great significance to conduct corresponding simulation studies.Compared with the fluid model,the particle-in-cell-Monte Carlo collision model has two advantages.One is that the influence of numerical dispersion and instability problems is insignificant,and the other is that it can accurately describe microphysical processes.Therefore,the breakdown characteristics on the gas side of dielectric window are simulated by using the particle-in-cell-Monte Carlo collision model.The two-in-one macroparticle merging method is introduced into the model,thereby greatly reducing the number of macro-particles tracked.Therefore,the whole breakdown process can be simulated and analyzed.The results show that the spatial and temporal evolution of breakdown under the variable macro-particle weight is in good agreement with that under the constant macro-particle weight.This suggests that the two-in-one macro-particle merging method is applicable under the simulation conditions of interest in this paper,i.e.,when the ratio of the effective electric field of microwaves to the pressure is between 1.76×10^(3)and 1.41×10^(4)V/(m·Torr).Since the yield of the secondary electron emission is much less than 1,gas ionization is the dominant mechanism of breakdown on the gas side of dielectric window.Electron ionization and electron diffusion lead the density and thickness of the plasma to significantly increase over time.The peak of electron density does not appear at the dielectric surface,but at a position of 100–150μm away from the dielectric surface.This is because a large number of electrons are deposited on the dielectric surface,and the accompanying self-organized normal electric field drives the electrons away from the dielectric surface.Because the pressure of background gas of interest in this work is higher than the critical pressure corresponding to the maximum ionization rate(

关 键 词：气体击穿 介质表面 高功率微波 粒子-蒙特卡罗碰撞模型 宏粒子合并方法 

分 类 号：O462[理学—电子物理学]