Dependence of gap voltage collapse during vacuum breakdown on gap geometry and plasma dynamics

In this paper experimental dependence of gap voltage collapse during vacuum breakdown on gap geometry and expanding plasma dynamics is investigated by breakdown development simulations. It is shown that voltage fall time dependence on gap geometry in the case of a uniform field gap and a point cathode-plane anode gap is due to different perveances that these two gap configurations have during breakdown. For a point anode-plane cathode gap the braking of cathode plasma emissive surface is responsible for much longer voltage collapse times. A large scatter in voltage fall time data is explained by dependence of cathode plasma expansion velocity on stochastic parameters of an initial cathode microplasma