INVESTIGATIONS OF CATHODE PHENOMENA IN PSEUDOSPARK DISCHARGES

The cathode phenomena during the conduction phase of a pseudospark dis charge are investigated with different cathode materials: Cu, Mo, Ni, Ta, and W/Re. The discharge gas was hydrogen with a gas pressure of 40 Pa. At a pulse duration of 2.7 mu s and a maximum current of 9 kA, i. e., at a transferred charge of 11 mC/discharge, mass erosion rates of the cathode materials showed no significant material dependence after 10(6) discharges. Fast framing photography (end-on, exposure time: 5 n s) of the light emission from the cathode surface revealed several sma ll spots simultaneously, distributed over a cathode surface of 1 cm(2) . The distribution of metal and hydrogen spectral lines at the cathode surface and in the gap were compared. Metal lines are localized on th e cathode surface, whereas the hydrogen Balmer beta-line is diffuse ov er the electrodes surfaces and the gap. Polished electrodes showed, af ter a single pulse, about 10(7) craters with 0.5-5 mu m in diameter. T his is leading to a local current density of about 10(8) A/cm(2) in a single crater.