Comments on the resistivity of high pressure, nanosecond, spark-gap switches

Summary form only given. An important class of compact, repetitive ultra-wideband pulsers makes use of the rapid resistance collapse of a spark gap, either self-breaking or triggered, as a closing switch to launch an electromagnetic pulse into a waveguide and ultimately to an antenna. The dynamics of the spark gap during its breakdown phase determine its resistance, inductance, and the risetime of the current, all of which will affect pulser performance. In this paper we show that the nanosecond-time-scale data of Sorensen and Ristic (1977) is not in fact well modeled by a constant /spl sigma/, particularly near and after current maximum. We show that good agreement with experiment requires that we account both for expansion-related cooling and radiation losses from the channel to obtain a conductivity that agrees well with experiment.