Measurements of vacuum arc threshold current for W cathode

Abstract

An experimental technique was developed to measure the threshold current of a vacuum arc with a tungsten cathode. Main point was to measure the arc cutoff current while it is powered by a slowly decreasing current pulse. The average value of the cutoff current for a series of discharges was assumed to be equal to the threshold current of the arc discharge. For a tungsten wire cathode, a value ~2.4 A was obtained, which is slightly higher than the standard value of the threshold current (1.6 A) obtained by Kesaev using the method of opening contacts. This can be explained by thorough preparation of the cathode surface.