Study on the mechanisms of anode plasma generation and ion acceleration in low-current pulsed vacuum arc discharge

Anodic vacuum arc ion sources find wide applications in electric propulsion and thin-film deposition systems, but the poor understanding of the generation and acceleration mechanisms of anode plasma imposes confinement on improving the performance of these devices. In this paper, the discharge process of low-current pulsed vacuum arc is self-consistently tracked using a 1D spherical particle-in-cell direct simulation Monte Carlo method coupled with an anode heat conduction model. The results show that in the vacuum spark stage, the electrons emitted from cathode spot can gain enough energy from the high pulsed voltage to heat anode to evaporate atoms and then generating anode plasma. The anode ions move toward the cathode under the electric field formed by high anode voltage, with kinetic energy being up to about hundreds of eV. As the discharge gradually transitions to arc stage, the low arc voltage reduces electrons heating on anode, and anode atoms are sputtered by cathode ions to sustain an anode arc. During the arc stage, the potential establishes a bimodal hump distribution. The newly generated anode ions are accelerated by anode potential hump and its pressure gradient to ∼103 m/s, which is one order of magnitude lower than that of cathode ions. These findings could be valuable in optimizing the design of an anodic arc ions source for efficiency improvement.