Progress Understanding Anode-Initiated Vacuum Insulator Flashover

There is often a dielectric separation barrier between vacuum and water-containing (or oil-containing) sections in pulsed power systems. This barrier must successfully hold off electrical breakdown as the applied electrical pulse is rising and delivering electrical energy to the downstream load. While breakdowns during the falling end of the pulse are somewhat understood to be electron cascade and saturation along the insulator (similar to multipacting) initiating at the cathode triple junction, the processes involved in breakdown during the rising pulse are not understood. One hypothesized process involves breakdown at the anode triple junction that is independent of the electron cascade process. A seed plasma then grows along the insulator towards the cathode. This presentation will describe recent efforts to better understand processes involved in anode-initiated flashover.