Decay of $\mathrm{SF}_6$ plasmas after nanosecond breakdown

The conductivity of $\rm SF_6$ afterglow plasmas following nanosecond breakdown at pressures of $60$–$400$ torr is studied experimentally. The measurement technique is based on probing the plasma with microsecond current pulses. A model for the decay of the plasma is constructed. The plasma decay is determined by ion–ion recombination of the weakly nonideal plasma, and three body collisions are taken into account in the calculated recombination coefficient by introducing an activity coefficient analogous to that for electrolytes. The effect of ion clustering is discussed.