Residence time and charge state of silver and zinc ions generated from microsecond vacuum arcs

One mm vacuum gaps with silver or zinc needle-cathode were fired by a 13 /spl mu/s duration sinusoidal arc or a 9 /spl mu/s duration exponentially decaying arc. Time-of-flight (TOF) ion measurements were made at variable ion extraction times after the arc ignition to measure the charge state and residence time of the ions. Ag/sup +/, Ag/sup ++/ and Ag/sup +++/ ions were generated from silver cathode and Zn/sup +/ and Zn/sup ++/ were generated from zinc cathode. Residual gas atom ions were generated together with the metal ions. Residence times of silver and zinc ions at the acceleration space, which was 15-25 mm apart from the needle cathode, were 5 /spl mu/s and 17 /spl mu/s, respectively, regardless the waveform of the arc current. Charge state fractions of silver and zinc ions were determined from the TOF ion currents and were compared with the results by other researchers.<
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