Onset voltage for corona pulses in gaseous Ar under high pressure and in liquid Ar

HV, applied to a point cathode (radius of curvature /spl sim/1 to /spl sim/8 /spl mu/m) in a nonpolar liquid, brings about a regular current pulse regime above a threshold value V/sub s/. This regime is similar to the Trichel pulse regime for corona in air. We present results of an investigation of this threshold voltage V/sub s/ in argon over a wide range of densities. In gaseous argon, the V/sub s/(P) values increase with pressure. In the liquid, V/sub s/ is independent of external pressure. The results show that V/sub s/ is mainly a function of fluid density N and cathode tip radius /spl tau//sub p/. The theoretical analysis of the phenomenon is carried out according to the criterion /spl int//spl alpha/(x)dx constant, where a(x) is the Townsend ionization coefficient. It is shown that if the dependence of V/sub s/ on N for low density gas is extrapolated into the region of liquid densities, it greatly exceeds the experimental values. The dependence of V/sub s/ on the fluid number density /spl sim/ is derived. Its variation is found to be non-monotonic at very high N values.<
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