2D Kinetic Simulation of Current-Carrying Plasma Expansion

A two-dimensional kinetic simulation of the expansion of the current-carrying plasma of the cathode spot of a vacuum arc is carried out. The modeling was performed by Particle-in-Cell and Direct Simulation Monte Carlo methods. The processes of ionization and recombination and Coulomb scattering are considered. Two fundamentally different solutions are demonstrated for an expanding plasma in an external electric field. The first solution is a "quiet" expansion of the plasma at a relatively low current. In which only ion-acoustic current instabilities arise, which do not lead to catastrophic consequences. In this mode, the plasma expands at a speed of ~ 10
⁶
cm/s, the electron temperature of the plasma reaches 3 eV, and the average charge state of ions (Cu) is ~ 2. In the second case, the current is large enough to excite the Buneman instability, after which the plasma plume decays and ions with relatively high energies scatter towards the anode and cathode.