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 emission, and electric field profiles in Ar and Ar+1% K hollow cathode discharges. The geometry and pressure are similar to those used in pseudosparks. The discharge was operated with a repetition rate of the order of kHz, an applied voltage in the range 300-600 V and with discharge current up to 1.5 A. Calculations were performed using a 2D, hybrid fluid-particle model developed previously [J.P. Boeuf and L.C. Pitchford, IEEE Trans. Plasma Sci. PS-19 286 (1991)]. Good agreement is found between the predictions of the model and the experimental results, and, in particular, both show an initial sharp peak (less than 100 ns in width) in the discharge current a short time after application of the voltage which is related to the expansion of the plasma into the hollow cathode. Further, the model shows that the sequence of events leading to the formation of the hollow cathode discharge is the same in the present experiments and in pseudospark switches operating at much higher voltages.