Effects of ion extraction on discharges in gridded ion source

Effects of ion extraction on gridded ion source discharge or the coupling between ion extraction and gridded ion source discharge are investigated for the first time by correlating the ratio of the ion impingement current (Ia) to ion beam current (Ib) with the total gray values extracted from images of discharge glows with and without ion extraction. The results indicate that, under equal power and gas pressure, discharges with high and low Ia/Ib values in the presence of ion extraction are, respectively, more intensive and weaker than those without ion extraction. The competing factors behind the coupling between ion extraction and ion source discharge are ion loss and energetic secondary γ-electron injection from the accelerator grid, which weakens and enhances ion source discharge, respectively.