Numerical simulation of transient anode plume formation and development in high-current vacuum arcs

The transient formation and development of an anode plume in high-current vacuum arcs are governed by the release, transport, and ionization of anode metal vapor and its interaction with the cathode-originated plasma. A two-temperature, multi-component model coupling electrons, ions, and neutral Cu/Cr vapor is developed. The neutral vapor is described by independent density and momentum equations, while a prescribed transient anode surface temperature, motivated by time-resolved experiments, is used to determine the evaporation flux. The results show that the vapor-rich region continues to propagate into the arc column even after the anode temperature begins to decrease. Preferential ionization occurs near the outer boundary of the vapor region, producing a transient plume structure with a neutral-rich core and an ion-enriched outer region. The dense neutral vapor reduces the local electron density and electrical conductivity, causing the current path to redistribute toward the plume boundary and surrounding plasma. The associated changes in plasma parameters modify the axial electric field and produce a nonmonotonic arc-column potential response. These results clarify the coupled vapor-transport, ionization, and electrical processes governing transient anode plume development.