Study on the influence of anode evaporation on discharge plasma in low-current short vacuum arc

Abstract

Short vacuum arc ion sources (inter-electrode gaps, 100–300 μm) demonstrate higher efficiency in promoting anode arc discharge compared to conventional millimeter-scale vacuum arcs (1–10 mm); however, the physical mechanisms by which anode vapor affects short vacuum arc discharge remain unclear. In this paper, we present a hydrodynamic model for low-current short vacuum arcs that includes the process of anode evaporation to study the impact of varying anode surface temperatures on the properties of cathode plasma, while also considering the processes of electron–vapor impact ionization and electron–ion recombination. The results reveal that as the anode surface temperature increases, the ionization rate at the anode rises, leading to an increase in ion density. On the anode side, the momentum exchange via ionization [min+(u→a−u→i) term] significantly exceeds the influence of the pressure gradient, resulting in a substantial reduction in ion velocity. Moreover, the increased work done by ion pressure leads to a rise in the ion temperature at the anode. In addition, when the anode surface temperature exceeds 2100 K, the net ionization rate on the anode is significantly greater than that on the cathode, which is more conducive to the generation of anode plasma. These findings are crucial for a deeper understanding of the generation mechanisms of anode plasma in short vacuum arc discharges.