Laser-Initiated Vacuum ARC for Heavy Ion Sources

Laser-triggered discharges have been considered for some time both for electron[1] and ion[2] sources. It has been recently shown that conventionally triggered metal-vapor vacuum arcs[3] can sustain even higher ion currents. In this paper, we point out that laser initiation permits arc operation in a high-current regime, and with geometry attractive for heavy ion sources. We present preliminary data on laser-initiated vacuum arcs [4] using carbon, copper, and tungsten cathode electrodes. Discharge current pulses of over 104 amperes with durations of up to 1 msec were employed to yield fully ionized source plasmas of liters volume with ion densities greater than 1013 cm-3. Electrode erosion rates were in the range of 10-4gm/C (the same order as in vacuum arcs) corresponding to ion injection currents in the range of 103 amperes.