Inert Gas Ion Beams from a Duoplasmatron Ion Source

Operational characteristics of a Duoplasmatron ion source were examined for millianmpere positive ion beams of Helium and Argon. Ion beam current was measured as a function of extraction voltage for various source arc and source magnet currents. With the source parameters fixed, the data exhibits a critical voltage, above which the target current saturates and is independent of extraction voltage. This saturation current is linearly dependent on the source arc and source magnet currents. Below the critical voltage, the target current can be described by a V3/2 dependency on extraction voltage. These observations indicate that the total ion current extracted from the plasma is only dependent on the source parameters. Results are compared for strong field and weak field extractor electrodes which confirm that the total current extracted from the plasma is independent of the extraction field strength.