Formation of beam-produced plasma by a forevacuum plasma-cathode source of a pulsed large-radius electron beam

Abstract

The research of formation of beam-produced plasma by a pulsed low-energy (up to 7 keV) large-radius electron beam, generated by a forevacuum plasma-cathode electron source based on a cathodic arc, is presented. Density of the beam-produced plasma depends nonmonotonically on accelerating voltage. A certain threshold voltage, which depends on the gas pressure and a distance from the extractor of the electron beam source, provides maximal plasma density. At a voltage higher than the threshold voltage, a further increase in the accelerating voltage leads to a decrease in the density of the beam-produced plasma, and the plasma density increases as the distance from the extractor of the electron source increases. These dependencies of plasma density are caused by change in the electron-impact ionization cross sections of gas. Plasma density increases with increasing electron beam current and increasing gas pressure. For the used forevacuum plasma-cathode source of the large-radius electron beam and experimental conditions, varying parameters of the electron beam provides formation of beam-produced plasma with cross-section radius up to 4–5 cm and plasma density up to 1017 – 1018 m-3 at distance from the extractor up to 19 cm.