The Motion Characteristics of a Single Cathode Spot in Removing Oxide Layer on Metal Surface by Vacuum Arc

Abstract

The motion of cathode spots plays a crucial important role in removing oxide layer on a metal surface by vacuum arc. In this paper, the characteristics of the motion of a single cathode spot on metal surface with oxide layer are investigated experimentally. Experiments are conducted in a detachable vacuum chamber. A hollow copper anode with a hole of $10~\text {mm} \times 10$ mm is used in order to observe the 2-D motion of the cathode spot. The motion of the cathode spot during the descaling process is photographed by a high-speed digital camera with an exposure time of $2~\mu \text{s}$ . Experimental results indicate that there are slow motion and fast motion of the cathode spot during descaling process, and the slow motion is the basic characteristic in most of the descaling time. The probability distribution of the cathode spot’s displacement and resident time, the average velocity, and the movement parameter $S^{2}/t$ are analyzed quantitatively. The results indicate that with the increase of gap distance or the decrease of oxide layer thickness, the cathode spot becomes more active.