Effect of Spacer Surface and Geometry on Surface Discharge in Gas Using PIC Simulation

The presence of spacer in a spark-gap system leads to a reduction in breakdown voltage. This paper studies the effect of spacer surface profile and surface protrusions on the breakdown voltage in compressed gases. Different spacer profiles comprising of conical angled insulators, bush-bar insulators, and double ended frustum insulators are used to study the effect of spacer profile on spacer efficiency under nanosecond pulsed voltage using particle-in-cell simulation. The effect of protrusions on the surface of the insulators is modeled to study the effect of teeth height on spacer efficiency. An increase in spacer efficiency from 86% in case of cylindrical spacer to 97% with negative angled and bush bar spacer is observed for a 20-mm spacer length placed between the spark gap electrodes with nitrogen as background gas.