First neutral beam injection experiments on KSTAR tokamak

Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; In, S. R.*; Lee, K. W.*; Jin, J. T.*; Chang, D. S.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; Park, H. T.*; Watanabe, Kazuhiro; Inoue, Takashi; Kashiwagi, Mieko; Dairaku, Masayuki; Tobari, Hiroyuki; Hanada, Masaya

The first NB (neutral beam) injection system of the KSTAR tokamak was partially completed in 2010 with only 1/3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly. Before the beam injection experiments, characteristics of the ion source were investigated. A minimum beam divergence angle was 0.8 . The ion species ratio was D:D:D=75:20:5. The arc efficiency is more than 1.0 A/kW. In the 2010 KSTAR campaign, the deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with the beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and the plasma stored energy were found.