Numerical Analysis of Ion Cloud Ejected from Thermal Plasma Contributing to Electron Emission in Vacuum Arc

Vacuum arc has been applied to valuable technology such as surface treatment of oxide layer and ion plating. Although it has been required to clarify the physics of cathode spots in vacuum arc for industrial applications, it has been unclear. The cathode spot in vacuum arc moves at high speed with evaporation from cathode metal caused by joule and ion heating. The evaporated metal is ionized, thermal plasma is generated above cathode. It is considered that the generated ions are transported from thermal plasma to outer region of cathode spot, ion cloud is generated and ejected from thermal plasma. The ion cloud produces high electric field induced between ion cloud and cathode, then field emission may occur, and the current path is changed. Based on this model, numerical analysis of ion cloud ejected from thermal plasma contributing to electron emission in vacuum arc is conducted in this research. As a result, ion cloud ejected from thermal plasma is calculated, high electric field contributing to movement of cathode spot was analyzed.