Monte Carlo simulation of microwave air breakdown in parallel plates considering electron-surface interaction

Abstract

In this paper, a Monte Carlo simulation method was proposed to investigate the initial cascade process of low-pressure microwave air breakdown. Calculations were performed by tracing electrons only, with the assumption that space charge was negligible. Two main electron generation mechanisms, electron-impact ionization and surface secondary electron emission (SEE), were introduced to simulate the initial breakdown phase more realistically. Detailed investigations were performed in a parallel plate waveguide operating at 9.4 GHz with pressures ranging from 0.2 Torr to 100 Torr. The results confirm that microwave breakdown is controlled by impact ionization at high pressures. However, as the gas pressure decreases, secondary electron emissions prevail against electron-neutral collisions, which leads to the sensitivity of the breakdown field on SEE. The threshold breakdown electric field obtained by the Monte Carlo method has been compared with experimental results, showing good agreement in the case where an appropriate secondary electron emission model is given. The developed Monte Carlo method provides an inexpensive way to determine the breakdown field and can be further applied to other microwave components of interest.