A theoretical model of the mercury and copper vapour arcs

Abstract

A model of the vapour arc is proposed which reconciles the characteristics of very high current density and low voltage drop. Two methods of electron emission are suggested to account for the exceptional current density: emission by excited atom bombardment, and thermionic field emission. The relative importance of these two processes is examined. In addition, account is taken of the effects of the transfer of ion momentum to the gas in the arc spot and the overall energy balance. The relationships derived from these mechanisms enable a quantitative description of the parameters of the arc spot to be made which only depends on the basic constants of the cathode material. Values of the arc parameters calculated for the mercury and copper arcs agree well with experimental measurements.