Plasma Sputter‐type Ion Source with Wire Electrodes for Low‐energy Gallium Ion Extraction

Low‐energy ions of gallium (Ga) and argon (Ar) were extracted from a plasma sputter‐type ion source system that utilized a tungsten (W) wire extractor geometry. The 90% transparent W wire extractor configuration had shown that the system was capable of producing an ion beam with the energy as low as 10 eV in a dc filament discharge and 50 eV in a radio frequency (rf) excited system. In the present investigation, Ar plasma was sustained in an ion source chamber through an inductively coupled 13.56 MHz rf power source. Negatively biased liquid Ga target suspended on a W reservoir was sputtered and postionized prior to extraction. Mass spectral analyses revealed a strong dependence of the $Ga+$ current on the induced target bias.