Conditioning of a vacuum gap by sparks and ion bombardment

Abstract

The influence of sparks and ion bombardment on the emitting properties of the electrodes and consequently on the breakdown voltage of a vacuum gap are investigated. The cathode used was either a stainless steel or a copper needle (radius of the tip 0.10 and 0.15 mm, respectively). The anode was a hollow hemisphere (radius 15 mm) of stainless steel. It appears that the field-enhancement factor β can be reduced by sparking from about 100 to 10 for the stainless steel cathode and from about 120 to 30 for the copper cathode. By ion bombardment β further decreases to 7 and 20, respectively. When the cathode is conditioned by ion bombardment, there is a deconditioning without breakdown at very high electric fields.