Random walk of cathode arc spots in vacuum

Abstract

The cathode spot movement of a vacuum arc with Al, Cd, Mo and Cu cathodes was investigated. Provided external disturbances are absent the cathode spot was found to move at random. The two-dimensional distributions of spot displacements can be described by a Rayleigh function. From the experimental data the average distances between cathode craters were deduced, leading to values of 2-3 times the crater diameter. Crater formation times, derived from the random walk data, were used to calculate the erosion rates of the metals listed. Good agreement was found between these data and earlier experimental results of cathode erosion rates and ion flows.