SPACE AND TIME-DEPENDENCE OF THE ELECTRIC-FIELD AND PLASMA-INDUCED EMISSION IN TRANSIENT AND STEADY-STATE HOLLOW-CATHODE DISCHARGES

We have performed time-resolved observations of the current, optical e mission, and electric field profiles in Ar and Ar+1% K hollow cathode discharges. The geometry and pressure are similar to those used in pse udosparks. The discharge was operated with a repetition rate of the or der of kHz, an applied voltage in the range 300-600 V and with dischar ge current up to 1.5 A. Calculations were performed using a 2D, hybrid fluid-particle model developed previously [J.P. Boeuf and L.C. Pitchf ord, IEEE Trans. Plasma Sci. PS-19 286 (1991)]. Good agreement is foun d between the predictions of the model and the experimental results, a nd, in particular, both show an initial sharp peak (less than 100 ns i n width) in the discharge current a short time after application of th e voltage which is related to the expansion of the plasma into the hol low cathode. Further, the model shows that the sequence of events lead ing to the formation of the hollow cathode discharge is the same in th e present experiments and in pseudospark switches operating at much hi gher voltages.