Particle-In-Cell Monte Carlo Collision Simulation of the Breakdown Initiating Process in Vacuum

The initiating process of vacuum breakdown is still unknown despite the efforts of many researchers in the long history of vacuum insulation. This paper reports the results of Particle-In-Cell Monte Carlo Collision simulation in the vicinity of an emitter of the electrons and the neutrals on the cathode. The radius of the emitter re, the temperature of the emitter T, product of macroscopic electric field and electric field enhancement factor β•Emac, and the electric field enhancement factor β itself are used as the parameters. It turns out that the current increased in some combinations of the parameters as the result of positive feedback of field emission, ion generation, electric field enhancement, increase in field emission electrons. All parameters affect whether the current increase or not. The radius of the emitter re is a key parameter to determine the occurrence of the current increase. This is because the density of the neutrals at the point where ionization occurs becomes larger with re.