Vapor stream in vacuum arcs

A summary of the experiments showing the existence of a high velocity vapor stream issuing from the cathode region of a vacuum arc is presented in this article. Velocities obtained by different methods are given. The article includes a review of the theories proposed to account for the vapor stream. Several theories proposed are shown to be inadequate, the one possible theory being based upon the presence of multiply charged ions which leave the cathode after neutralization with a high velocity.