On the negative anode voltage fall of high-current vacuum arc: PIC-modelling results

The numerical modelling of the interaction of vacuum arc plasma with the anode surface has been performed by PIC method. It has been found that the anode potential fall remains negative even for the electron drift velocity large than thermal velocity. Two regimes of plasma anode-surface interaction have been analyzed in modelling - a 'steady-state' one and a 'turbulent' one with the plasma micro-instability developed. For the 'steady-state' regime approximate expressions of the anode potential fall and the energy flux have been derived from the modelling results. For the 'turbulent' regime that naturally corresponds to a large electron drift velocity, the enhancement in the negative anode potential fall as well as in the plasma electron effective temperature have been found.