Evaluation of plasma transport in a multipole ion source and its impact on discharge performance

In this work, the current distribution at the four magnet rings of a cylindrical 16-cm diameter mild steel ion source discharge chamber was studied. The current distribution measurements were made using thin, electrically isolated collector electrodes affixed to each magnet ring. Current collected at the magnetic cusps as well as the intervening anode material was quantified as a function of discharge plasma conditions. Discharge efficiency and stability were investigated as a function of current distribution. This work is aimed at obtaining a more complete understanding of plasmas losses to the wall surfaces in multipole ion sources.