Numerical simulation of cathode process and plasma characteristics in diffuse current attachment vacuum arc with heated cathode

Vacuum arc is an important multi-component plasma source. Under heated-cathode conditions, the ability of electron emission of the cathode material can significantly modify the current attachment pattern on the cathode surface, enabling a transition from conventional cathode-spot discharge to diffuse current attachment (DCA). This transition enhances the stability and controllability of plasma parameters. In this paper, a comprehensive numerical model is developed for vacuum arc with a heated cathode. The model focuses primarily on current conservation and electron energy conservation near the cathode side and plasma characteristics of the arc column in the DCA mode, and it further performs a comparative analysis with the cathode-spot mode in terms of temperature. The simulation results show that the cathode work function and cathode temperature, by modulating the ability of electron emission, directly affect the cathode electric field strength, cathode voltage drop, and electron temperature. In the DCA mode, variations in the electron temperature induced by changes in the cathode voltage significantly influence the species distribution near the cathode. Compared with the cathode-spot discharge mode, the net energy flux density in the DCA mode is negative, indicating an effective cooling of the cathode surface. This work provides a theoretical description of the physical mechanisms responsible for different discharge modes exhibited by various cathode materials and offers guidance for the design of controllable multi-component vacuum arc plasma source.