Study of Shock Wave and Magnetic Pressure Effects on the Rail Gap Switch Surface Used at the APF Plasma Focus Device

Abstract

Whereas high voltage and current create a rough environment for switch electrodes in pulse power technology, the switch requires the most maintenance or replacement after a short time. In this paper we investigate the effects of magnetic and shock pressures created by high power electric arc between a rail gap switch with copper electrodes at the APF plasma focus device. As studied by others, the shock pressure is some order of magnitude higher than the magnetic pressure after electric arc generation. We calculated the magnetic pressure, electric arc radius, time dependent arc velocity, and also time dependent shock pressure created by an oscillating current discharge applied across the rail gap electrodes surface. Modeling included a MathCAD analysis of the diverging wave front through the electrode and the results show that the shock wave pressure induced after the electric arc has a serious destructive effect on our switch surface.