Split process of cathode spots in low-pressure arc on Fe+C surface with oxide layer

Summary form only given: A cathode spot in a low-pressure arc has remarkable characteristics. For example, the cathode spot moves around the metal surface very fast and a cathode spot can remove an oxide layer. So, the cathode spots of low-pressure arcs have been used for cleaning metal oxide surfaces. However, the influence of an oxide layer on cathode spot movement remains unclear. In this research, the cathode spot movements on the surface of oxide layer and metal surface were measured to determine the cathode spot movement. Experiments were using a Fe+C cathode and a cylindrical copper anode. A highAcircnot speed video camera recorded the cathode spot movement. The cathode spot movement was generated mainly on the boundary layer, but sometimes on the processed surface. The first spot remains at the boundary when the cathode spot splits; the second spot moves on the bulk surface and reappears at a different boundary. Therefore, the cathode spot does not appear suddenly, it moves continuously during the split process. The removal process of oxide layer does not always have priority for cathode spots, but the oxide layer plays an important role for cathode spot existence because of oxide layer vaporization.