Influence of the gas type on the electrical strength of the accelerating pro-gap of the fore-vacuum plasma source of electrons

The electrical strength of the accelerating gap of a fore-vacuum plasma electron source is compared for different working gases: argon, nitrogen, oxygen, and helium. The dependences of the limiting electron emission current, above which breakdown occurs, on the voltage across the accelerating gap are presented. It has been established that the limiting emission currents are determined by the thickness of the emission electrode, the diameter of the holes in it, as well as the gas type and pressure. It has been established that for all gases the limiting emission currents decrease with increasing pressure. The limiting pressures, when exceeded, breakdown occurs, decrease in the series: helium, oxygen, nitrogen, argon. For different experimental conditions, the dependences of the limiting emission currents on the accelerating voltage can be both monotonically growing and containing an extremum.