Effect of total voltage on breakdown in vacuum

The results of a series of high voltage breakdown tests between metal electrodes in high vacuum are reviewed, with consideration of the observed inverse relation between cathode gradient at breakdown and gap length. This leads to the conclusion that the current that flows between electrodes as the conditions for high voltage breakdown are approached must involve positive ions from the anode. The deposition of anode material upon the cathode, which would occur in the event of such positive-ion emission, was found to take place. As final proof of this hypothesis, interelectrode current at constant cathode gradient was found to vary with voltage.