Stability of electron beam generation by forevacuum-pressure plasma-cathode electron beam source based on a cathodic arc

We describe our experimental research on the stable generation of large-radius pulsed high-current electron beams using a forevacuum-pressure plasma-cathode electron beam source with cathodic arc plasma generation. We find that increased gas pressure and the use of gas with a higher ionization cross-section considerably decrease the stable emission current due to loss of electric strength of the acceleration gap (breakdown). Increased pulse duration results in a decrease in the emission current, but the influence of the gas species and its pressure remains for all pulse durations. There is an extremum in the dependence of emission current on the acceleration gap length and the optimum gap length depends on the gas pressure and the kind of gas. The experiment results can be explained by the effect of back-streaming ion flow, which charges dielectric inclusions on the emission electrode (anode grid) and thereby amplifies the electric field.