A PIC-MCC numerical approach for studying the effect of pulse steepness on vacuum flashover

Study on nanosecond pulse flashover characteristics of vacuum insulator surface is extremely significant for designing reliable pulse power devices. The rising steepness of pulse voltage greatly affects the flashover process. In this study, a two-dimensional model based on secondary electron emission avalanche (SEEA) scheme was established to study the relationship between pulse rising steepness and flashover performance. Particle-in-cell (PIC) method was used to describe multiplication and propagation behaviors of the charged particles during the flashover process. And collisional ionization process between primary electrons and desorbed gas was described by the Monte Carlo collision (MCC) method. The number evolution, distribution of charged particles, and field distribution at different moments during the flashover process are successfully presented in the simulation. Furthermore, the model shows that higher pulse voltage rising steepness will lead to higher flashover voltage, which accords well with our group's previous experimental results.