The influence of gap distance on cathode spot motion in removing oxide layer on metal surface by vacuum arc

The motion of cathode spots plays a crucial important role in removing oxide layer on metal surface by vacuum arc. In this paper, the characteristics of a single cathode spot motion were investigated experimentally. Experiments were conducted in a detachable vacuum chamber. A hollow copper anode with a hole of 10×10mm was used in order to observe the two-dimensional motion of cathode spot. The motion of cathode spot during the descaling process was photographed by a high-speed digital camera with an exposure time of 2 microseconds. The influence of gap distance on the motion of cathode spot was investigated. The probability distribution of the number of times that cathode spot stayed at a position and the probability of cathode spot displacement indicated that with the increasing of gap distance, cathode spot became more active.