Mechanisms of electrical discharges in high vacuum at voltages up to 400 000 V

Abstract

High‐voltage electrical discharge mechanisms were studied in a stainless‐steel and alumina‐ceramic vacuum system evacuated by an orbitron getter‐ion pump. The high‐voltage terminal was charged by a pelletron generator, and its voltage was measured by a generating voltmeter. A moveable ground plate was used to vary gap length. For gaps larger than 2 in., the voltage was limited by regularly spaced discharge pulses and conditioned to a maximum of 230 kV independent of field strength. Mass‐spectrometer studies were made of ions emitted from the terminal during discharges with positive and negative terminal polarities. Ions ejected from the terminal by a beam of Na⁺ ions were also examined. Results of these and other studies led to the conclusion that the regularly spaced discharge pulses were the result of an ion‐exchange multiplication process. Measurements demonstrate that gas hinders this mechanism by stripping electrons from negative ions. Electrons were found to be only by‐products in the multiplication process. In contrast to the whisker mechanism, the ion‐exchange multiplication was found to depend only on total voltage and not on electric field strength. Experiments with gaps smaller than 2 in. supported the conclusions that the voltage is limited by field emitting whiskers and the presence of gas damages these whiskers.