An investigation of pre-breakdown cathode microcratering

Abstract

Electric fields, pulsed or dc, can initiate the formation of protrusions on tungsten hairpin cathodes used with plane anodes of varying materials. Topographical studies of both electrode surfaces, using scanning electron microscopy, have now shown that these protrusions appear to be the irregular lips of microcraters. This damage is almost entirely confined to the cathode surface, and its occurrence appears to depend upon the material initially used for the anode; a stainless steel anode having ten times the probability of giving a stable electrode pair than a copper anode. Neutron activation analysis failed to detect any anode material on damaged cathodes.