Plasma parameters of an arc cathode spot at the low-current vacuum discharge

This paper is devoted to the results of an experimental study of plasma parameters of cathode spot burning on a liquid-metal cathode in vacuum at a low-current (less than 200 A) vacuum arc discharge. Picosecond laser interferometry and absorption shadow imaging were used in a single experiment. Plasma fragments as dense as 10/sup 26/ m/sup -3/ were observed at discharge currents less than 50 A. Such fragments were never observed in arc discharges with currents higher than 100 A or in the breakdown stage of the discharge.