SI streamer initiation and breakdown in pressurized technical air in sphere-plane geometries

Abstract

The breakdown properties of air are well studied at ambient pressure. For higher pressures, less information can be found in the literature. In this paper, switching impulse breakdown properties in technical air as a function of pressure are investigated. The study focus on a spherical electrodes with 30 mm and 10 mm diameter with a distance to a ground plane of 100 mm. From prebreakdown photomultiplier signals and photographs taken with an ultrahigh-speed camera also the initiation voltages are measured. From the analysis of the results, streamer initiation fields as well as propagation fields are extracted. As expected, the breakdown voltages as well as the initiation voltages increases with pressure, for both positive and negative polarity. Streamer integrals are used to evaluate the initiation fields. The observed streamer initiation voltage agrees well with streamer integral theory in the studied pressure range 1 Bar to 6 Bar. The pressure dependence of streamer propagation is also analyzed and is found to approximately scale linear with the pressure for both polarities.