An Interpretation of Pressure and High Velocity Vapor Jets at Cathodes of Vacuum Arcs

Tanberg's conclusion, that the evaporating vapor from the cathode of a copper vacuum arc escapes with a temperature of about 500,000^∘{}K, which is based upon measurements of the repulsive force against the cathode, is shown to be unnecessary. The observed pressures can reasonably be explained in terms of the "accommodation coefficient" of the incoming Cu ions. It is thus shown that the observed pressures are accounted for if the positive ions retain about 2 percent of their incident kinetic energy after neutralization at the cathode.