Three-dimensional hybrid plasma modeling of anodic sputtering in vacuum arcs

Abstract

In this paper, a three-dimensional plasma jet model based on a hybrid algorithm was developed to study the sputtering phenomena during the interaction between the vacuum arc plasma jet and the anode. To improve the balance between accuracy and efficiency of the simulation model, heavy particles (ions and atoms) were treated as particles, while electrons were considered as a massless fluid. The Monte Carlo collision method was used to model inelastic collisions between heavy particles and electrons. In addition, the anode in this model did not only act as a passive current collector, but may also emit atoms into the gap when hit by heavy particles. The simulation results show that the anode is sputtered by the impact of high-speed ions from the plasma jet, and a stream of atoms is generated from the part of the anode surface that is in contact with the plasma. Some of the sputtered atoms are ionized into Cu1+ ions by colliding with electrons during their movement from the anode to the cathode. As a result of the production of these new ions, the Cu1+ ions density may exhibit a bimodal distribution with one peak near the cathode and the other near the anode. Furthermore, the ions can be divided into two groups according to their velocity distribution: high-speed ions moving from the cathode to the anode and low-speed ions moving in the opposite direction. These findings reveal that the sputtering process between the plasma and the material surface has a great influence on the energy distribution function of the ions in the plasma, which has often been ignored by researchers in previous studies.