Study of wire explosion in vacuum at different electrode polarities

This paper presents experimental results on electrical explosions of thin tungsten wires at current rise times of several tens of nanoseconds at wire currents of 0.04-0.4 kA. The experiment was performed for both negative and positive polarity of the high-voltage electrode. In addition to conventional current and voltage measurements, the current to a cylindrical grounded screen placed between the exploded wire and the return conductor was measured. The screen current was detected only for a 6-mum wire exploded with the high-voltage electrode being at a negative potential. In all other test modes (a 6-mum wire exploded at positive electrode polarity, 30.48-mum wires exploded at negative and at positive electrode polarity) there was no current to the screen. A model of the discharge initiation during a wire explosion in vacuum has been proposed which is based on the supposition that surface discharges develop around the wire along the electrode surface. The presence of plasma-emitted electrons at the cathode surface makes it possible to interpret the experimental results on wire explosions at different electrode polarities reported both in this paper and in previous publications.