Plasma and electrode interactions in short gap discharges in air II. Electrode effects†

Electrical breakdown in a matched 125 ω spark chamber has been studied, both by time resolved spectroscopy and by examination of the electrode surface damage using a scanning electron microscope. Short duration arcs in air, at atmospheric pressure and preceded by a glow discharge, hove been observed electrically and spectroscopically. Damage on the cathode due to the high current glow discharge was negligible compared with the destructive cratering due to the arc. A tentative model, using ion bombardment, explains the observed cathode damage. The plasma and electrical aspects of this study are reported in the companion paper; I. Plasma effects.