Stationary vacuum arc on the hot non-thermionic cathode

A vacuum arc with a stationary diffuse spot on a solid chromium cathode has been studied. The arc current was 30-220 A, cathode temperature 1800-2100 K. The mean current density on the cathode was 10-10/sup 2/ A/cm/sup 2/. The part of thermionic current at the cathode was less than 0.1% from the arc current. Observations of cathode surface during arcing with the help of laser monitoring did not discover noticeable arc influence on the cathode. The experimental data on the heat flow from plasma to cathode and the evaporation rate of the cathode in principle allow the conclusion that the charge transfer on the cathode surface is provided presumably by ion current.