Comparison of H−/D− measurement in the magnetically filtered region of the large negative ion source

Abstract

Characteristics of D− production are experimentally compared with that of H− production, both in extracted negative ion beam and in negative ion density in the extraction region, which is the magnetically filtered region in front of the plasma grid. Extracted D− beam current reduces to 1/2–1/3 in the case of H− beam and electron current extracted simultaneously with D− beam increases more than twice as the case of H2 discharge at the same filling gas pressure. Variation of electron density in the extraction region is similar to extracted electron current. Small reduction of D− density in the extraction region is observed, compared to H− density at the same position, but the ratio of reduction differs from the case of extracted ion beam. When the filling gas pressure is raised, D− density and beam current almost linearly increase, similar to the case of H−.