Ion charge state distributions of pulsed vacuum arcs - Interpretation of their temporal development

Ion charge states of vacuum arcs are enhanced at the beginning of each are pulse. The ion charge states drop with time and become steady-state after about 100 mu s, with some dependence on the cathode material. A reduction of ion charge states has been observed at the end of each are pulse. In this note it is shown that the charge-state-dependent ion drift velocity in the plasma expansion zone contributes to the effect measured by the time-of-flight method, although it is not solely responsible for it. A quantitative evaluation as well as literature data of other measuring methods prove the physical significance of the effects observed.