Numerical study on the effects of discharge parameters on vacuum arc plasma

Abstract

Studying the characteristics of vacuum arc plasma within a wide range discharge parameters is vital for vacuum arc applications. In this study, specific parameters of vacuum discharge, including cathode temperature ranging from 6000 to 8000 K, emitted electron temperature spanning from 0.69 to 2.5 eV, and arc burning voltage within the range of 16-30 V, have been selected to analyze the effects of these parameters on the cathode erosion, cathode potential drop, and ion velocity. A validated one-dimensional spherical PIC-DSMC cathode spot model is employed to simulate the generation and expansion of vacuum arc plasma. The results indicate that increasing the cathode temperature and the emitted electron temperature both enhance the cathode eroded mass. However, this mass diminishes as the arc voltage increases due to more Cu ions and Cu atoms return to cathode under the high cathode potential drop and charge exchange collision, respectively. The cathode current density remains nearly constant within the explored range of cathode temperature, but increases as shifting the emitted electron temperature and arc voltage. A higher cathode current density, coupled with the positive cathode plasma resistance, induces a higher cathode potential drop that significantly surpasses the cathode sheath voltage. Furthermore, a higher ion velocity is observed at increased arc voltage due to the higher cathode current density generate stronger electron friction for accelerating ion. These findings could be valuable in designing a suitable arc voltage in vacuum electric thrusters to enhance thrust.