Two modes of vacuum flashover process under pulsed voltage

Vacuum flashover process can be influenced by various factors, such as gap length, applied voltage form, electric and magnetic field structures, and so on, leading to different flashover voltages and flashover times under a pulsed voltage. Particle-in-cell (PIC) simulation results in this paper show two typical vacuum flashover modes: (a) the area of high space charge density appears after electrons run across the gap and extends from the anode to cathode and (b) the area of high space charge density appears before electrons run across the gap and extends from the middle to both ends of the gap. In order to verify the PIC simulation results, a probe that measures the change in the electric field between the gap is embedded in the anode, the experimental waveform of which shows different features when the shape of insulator is different. Simulation results and experimental waveforms indicate that the flashover process of certain cylindrical insulators corresponds to the first mode, while the flashover process of certain conical insulators with an acute angle between the cathode and dielectric corresponds to the second mode. Published under an exclusive license by AIP Publishing.