Beam current deterioration in a 13.56 MHz RF negative ion source

Abstract D-Pace is developing a 13.56 MHz external planar antenna-powered RF ion source for producing negative ions (H - , D - ). The cesium-free RF ion source is expected to operate with lower maintenance cycle compared to D-Pace's TRIUMF-licensed filament ion source. The present challenge with the RF ion source is the deterioration in H - beam current extracted from the ion source during its operation over several days. The reasons behind the beam decay are not yet fully understood. Sputtering of the copper plasma chamber and the AlN RF window are considered likely causes for the beam decay. Experimental observations related to the RF ion source beam deterioration are presented in the current paper.