Plasma density decay of vacuum discharges after current zero

The knowledge of the physical processes around current zero and their modeling is important for the development of vacuum interrupters towards higher switching capacity and higher voltages. One essential feature is the recovery of the arc gap after current zero from the well-conducting state of the high-current plasma to the isolating state of the cold gap. Like in other switching media, there is still plasma present in the switching gap at current zero, which needs time to recombine and disappear. The presence of post-arc charge is associated with post-arc current under the influence of the transient recovery voltage, which in turn interacts with the surrounding network. As the charges carried by the post-arc current leave the gap, the post-arc current also influences the plasma decay. A simulation of this combined behavior needs an adequate mathematical post-arc model as well as the knowledge of data of the charge-carrier densities and their decay. It is the aim of this work to determine the necessary data, based on a simplified one-dimensional post-arc model, and to compare model calculations with experiments.