Hybrid Modelling of Asymmetric Sheath Expansion after Current Zero in Vacuum

The dielectric recovery process of the vacuum arc is primarily influenced by the expansion of the sheath, which, in turn, is determined by the behavior of particles in the post-arc stage. Previous simulation studies have assumed a uniform distribution of plasma, which is not consistent with realistic conditions. The objective of this paper is to simulate the sheath expansion of a nonuniform and asymmetric plasma using a hybrid plasma model as the initial condition for the post-arc stage. We simulated the sheath expansion under the conditions of a single cathode spot and multiple cathode spots. In the case of a single spot, ions diffusing radially caused a more rapid sheath expansion. In the case of multiple spots, an asymmetric sheath formed due to the asymmetric spots. Our model provides a more accurate simulation of the sheath expansion process in the post-arc phase.