Discharge in a long metal tube with an electron beam generated by a forevacuum plasma–cathode electron source

Abstract

We describe our investigations of the current distribution in a non-self-sustained hollow-cathode glow discharge in a long metal tube. The discharge is initiated and sustained by injecting an electron beam generated by a forevacuum-pressure plasma–cathode electron source into the tube. It is shown that the distribution of discharge current along the inner sidewall over the tube length and, correspondingly, the distribution of plasma density along the tube depend primarily on tube geometry and electron beam current. The character of the discharge current distribution is determined by the ratio of contributions to ionization by beam electrons and by secondary electrons emitted from the tube bottom (if the lower end of the tube is closed) and from the tube sidewall. These processes may lead to a non-monotonic distribution of discharge current with a minimum in the middle. Increasing the discharge current levels out this minimum, improving the uniformity of the current distribution over the tube length.