Research and Development Activities on Negative Ion Sources

The research and development (R&D) activity on the negative ion sources at the National Institute for Fusion Science is described. During the R&D period from 1989 to 1998, intensive experimental investigations were carried out at a test stand with three sizes of ion source, 1/6, 1/3, and full size. Although comprehensive research had been carried out, there remained some problems on the Large Helical Device (LHD) beamlines. To resolve those problems, the ion sources and beamlines have been improved in several successive steps since the beam injection experiment of LHD started. Over the past decade, the injection energy, power, and reliability have been increased; the maximum energy now exceeds the 180-keV design value and the maximum injected powers reach 6.8 and 5.5 MW from beamlines 1 and 2, respectively.