Effect of transverse magnetic field on erosion rate of cathodes of rotating arcs

It has previously been shown that when arcs rotate over a copper cathode the erosion rate of this electrode rises and falls as the arc velocity is increased. In the paper it is shown that it is the magnitude of the transverse magnetic field and not the arc velocity, which determines the successive minima and maxima in the erosion rate. The erosion rates of cathodes of a number of materials are examined and for each the factor of increase in magnetic field strength is determined which is sufficient to cause successive minima and maxima in erosion rate. It is suggested that these variations, and similar variations found when the cathode-cooling-water flow rate is increased, arise from related phenomena in the oxide film on the cathode surface.