THE ELECTRICAL BREAKDOWN OF SMALL GAPS IN VACUUM

Abstract

An investigation of the electrical breakdown in vacuum of small gaps subject to contamination by diffusion pump oil showed that the most consistent results were obtained when electrodes were conditioned by a hydrogen discharge. Even with this method of conditioning a few preliminary sparks were usually required before the breakdown voltage reached a plateau level, so that the vacuum discharge itself could affect the final values obtained. The circuit parameters which controlled the discharge current were found to influence the magnitude and consistency of the breakdown voltage appreciably.Direct, alternating, and impulse voltage tests showed that the time for which voltage was applied to the vacuum gap influenced the breakdown voltage, and curves are presented which give the insulation strength of the gap. Two possible explanations of the time dependence of the breakdown voltage are given.