Electron Distribution in Low-voltage Arcs

Abstract

THE plasma properties of a low-voltage arc will depend on the way in which electrons are distributed through it. The electrons, as in other hot cathode discharges^1,2, occur mainly in two groups, one consisting of almost monoenergetic electrons which have fallen through the cathode sheath and acquired random direction in a few mean free paths with little change of energy, the other much slower and near-Maxwellian. As part of a study of hydrogen thyratrons, measurements have been made of the concentrations of both groups in a similar device without control electrode, using Druyvesteyn's probe method³. We find that they can be accounted for by diffusion theory and report here briefly some results of general interest which have been obtained for the fast group. Comparable results have been obtained for the slow.