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

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.