Cathode spots jump of low pressure arc

Summary form only given. Remarkable characteristic of cathode spots of low pressure arc can remove the oxide layer preferentially. Recently, cathode spot of low pressure arc has been used for cleaning metal oxide surface before the thermal spray or surface modification. However, there is few reports on the cathode spot movement or the oxide removal process. The experiment carried out by using the SS400 cathode work piece and the used cylindrical copper anode. To use cylindrical copper anode is enable to observe the cathode spots movement from above. The cathode spot movement taken by high speed video camera is observed and analyzed by using the plasma image processing (PIP). The high speed video camera can be taken picture at 1 ms per flame. The surface of work piece were covered with thick oxide (10 mum). The oxide layer thickness is analyzed by using microscope. The surface of work piece after processing was analyzed by using the laser microscope. The cathode spot moved continuously when the cathode spot removes oxide layer. After that, the cathode spot movement is not continuously. The cathode spot sometimes jumps. The reason of jump is cathode spot becomes instability. The abnormal glow discharge generates when the cathode spot jump. As the processing time increases, the distance of jump becomes large. There is relation between the cathode spot movement and the cathode surface roughness. When the roughness is large, the jump of cathode spot is large. And when roughness is small, the jump of cathode spot is small