大气条件下的沿面闪络等离子体演化过程研究

Evolution of Plasma Flashover on Ceramic Surfaces in Atmospheric Environment:A Simulation and Experimental Study

电子器件在大气环境下发生沿面闪络导致工作失效是限制其性能的瓶颈问题之一。本文基于高速相机诊断得到了大气条件下陶瓷沿面闪络发展过程,并与真空沿面闪络过程进行了比较。然后基于二维网格粒子法耦合直接模拟蒙特卡罗法(PIC-DSMC)建立了相应的仿真模型,得到了大气条件下陶瓷沿面闪络过程中电子和离子数密度分布演化特性,分析了大气条件下沿面闪络过程中等离子体通道的形成与竞争特性,并与实验结果进行了验证,阐明了大气条件下沿面闪络过程的物理机制,为进一步深入理解沿面闪络问题提供了支撑。

The growth of plasma flashover on insulation ceramics surfaces,in vacuum and atmospheric environments,was mathematically modeled,theoretically analyzed,experimentally evaluated with high-speed CCD camera,and numerically calculated in particle-in-cell direct simulation Monte Carlo(PIC-DSMC)method.The simulated results show that the field emission and ionization of air molecules induced by collision of high energy electrons have a major impact.The simulated and measured results were in good agreement.For instance,the initial electron avalanche"channel"on ceramic surface,generated by electron emission from the metal/air/insulator triple-interface points on the cathode,rapidly grows into the dominant plasma avalanche"channel",originated from electron-induced ionization of gaseous molecules and"drifting-away"above ceramic surface,consequently,no such drifting-away of plasma channel may occur in vacuum.Moreover,the desorption-gas density,much smaller than that of air(~1025 m-3),is too low to affect the flashover in air.