THE PLASMA STATE IN THE SURROUNDINGS OF A MULTI-CATHODE-SPOT VACUUM-ARC

A stationary, two-fluid model with spherical symmetry to describe the region surrounding the electrodes of a multi-cathode-spot vacuum are i s presented. For typical values of are parameters, there is a weak cou pling between ions and electrons and an analytical approximation for t he physical quantities of the plasma can be developed. An important fe ature of this model is the prediction of a voltage profile outside the electrodes which causes an extra acceleration of the ions emerging fr om the interelectrode plasma.