Current Injection and Light Emission in Liquid Argon and Xenon in a Divergent Electric Field

Unipolar injection currents originating from a point electrode immersed in LAr or LXe have been observed as functions of voltage and polarity. The dependence was found to be governed by space charge limitation. Ion mobilities were deduced from the analysis of the positive injection currents. Time resolved measurements of the light emission demonstrated that the negative injection current consisted of pulses, similar to Trichel pulses in air corona. Positive currents produced continuous light emission. The results are discussed on the assumption that a gaseous discharge is formed around the point electrode.