Investigations of carbide electrodes in high-current pseudospark switches

Abstract

Semiconducting carbides, S i c and BC, were tested as electrode material in pseudospark switches. Typical parameters of the test circuit were a charging voltage of 20kV, a peak current up to 120kA and a pulse length of 5ps (weakly damped sinusoidal pulse shape). In comparison to metal electrodes no differences in the electrical signals were detected. Optical investigations with a fast shutter let assume, that the discharge starts on axis. At later times the discharge plasma is homogeneously distributed over the total carbide surfaces of the electrodes. No cathode spots were observed. The erosion rate is low in comparison to molybdenum electrodes. The lifetime of the switch is enlarged as first tests show, but the holdoff voltage is limited due to field enhancement at the triple point metal, carbide, and gas.The pseudospark [ I ] is a low pressure gas discharge on the left side of the breakdown characteristic which is comparable to the PASCHEN curve. In recent years, pseudospark switches have been developed for several applications [2,3,4]. Lifetimes of up to 10' discharges