The behaviour of the ion current at the extinction of high current vacuum arcs

Ion currents extracted from high current arcs in a vacuum have been studied by a retarding field analyser and Langmuir probe. The current of the discharges reached up to 10.5 kA, and the electrodes consisted of CuCr. It was observed that the extinction of the arc is already announced in the signal of the ion current before the true current interruption. This reaction time, which depends on the arc current, is discussed. After the arc interruption, the ion current decay can be approximated by an exponential relation. The decay time of the ion current is in agreement with the results of post arc current measurements after extinction of high currents