ION CHARGE-STATE DISTRIBUTIONS OF PULSED VACUUM ARCS - INTERPRETATIONOF 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-sta te 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 i on drift velocity in the plasma expansion zone contributes to the effe ct measured by the time-of-flight method, although it is not solely re sponsible for it. A quantitative evaluation as well as literature data of other measuring methods prove the physical significance of the eff ects observed.