Intermediate and high-mass ion beams from a 10-cm Duopigatron

Abstract

Experimental studies of a 10-cm Duopigatron as a source of argon, krypton, and xenon ion beams are reported. Source plasma instabilities are examined, and the mass dependence of oscillation frequencies and instability onset conditions are determined. Arc current and density oscillations are found to be associated with ion acoustic fluctuations with frequencies scaling as 1/M 1/2 . Langmuir probe measurements within the source plasma double layer are used to indicate the physical mechanism responsible for the observed large-amplitude are current shifts. Ion beams have been extracted at energies up to 18 kV, and drain currents up to 540 mA for argon, 440 mA for krypton, and 520 mA for xenon have been achieved with source plasma densities in the range 10 11 –10 12 cm –3 . Excellent agreement with existing theoretical models has been obtained in the mass and density dependence of the extraction current, as well as the voltage at which transition from space-charge limited to ion saturation emission occurs.