Mevva ion source operated in purely gaseous mode

We have operated a vacuum arc ion source in such a way as to form beams of purely gaseous ions. The vacuum arc configuration that is conventionally used to produce intense beams of metal ions was altered so as to form gaseous ion beams, with only minimal changes to the external circuitry and no changes internally to the ion source. In our experiments we formed beams from oxygen (O+ and O-2(+)), nitrogen (N+ and N-2(+)), argon (Ar+), and carbon dioxide (C+, CO2+, O+, and O-2(+)) at extraction voltage of 2-50 W We used a pulsed mode of operation, with beam pulses similar to50 ms long and repetition rate 10 pulses per second, for a duty cycle of about 50%. Downstream ion beam current as measured by a 5 cm diameter Faraday cup was typically 0.5 mA pulse or about 250 muA time averaged. This time averaged beam current is very similar to that obtained for metal ions when the source is operated in the usual vacuum arc mode. Here we describe the modifications made to the source and the results of our investigations. (C) 2004 American Institute of Physics.