A periodic table of ion charge-state distributions observed in the transition region between vacuum sparks and vacuum arcs

Ion charge-state distributions have been measured with high time resolution for short (20 mus) and long (250 mus) vacuum discharges of 300 A. Charge-s tate data for 3 mus after discharge ignition and quasi-steady-state values are given for most conductive elements in a Periodic Table, including data for a few elements (rhodium, europium, and terbium) that were never before reported in the literature. Ion charge states are significantly higher at t he beginning of the discharge and decay to their quasi-steady-state are pla sma values. It was found that the mean ion charge states can be fitted by f unctions of the form (Q) over bar = (Q) over bar (t --> infinity)[1 + A exp (-t/tau)] where A is an enhancement function that depends on the power dens ity. For the present conditions, A similar to 1 and tau similar to 50 mus.