Progress in the development of long pulse negative ion sources in N-NBI for JT-60SA and ITER

Hiratsuka, Junichi; Hanada, Masaya; Kojima, Atsushi; Umeda, Naotaka; Kashiwagi, Mieko; Yoshida, Masafumi; Nishikiori, Ryo; Ichikawa, Masahiro; Watanabe, Kazuhiro; Tobari, Hiroyuki

New technologies for the high power and long pulse negative ion beam sources have been developed with R&D activities on the JT-60SA ion source and the ITER prototype accelerator in Japan Atomic Energy Agency. R&D progress of the temperature control of the plasma grid resulted in the long pulse negative ion production of 100 s with high current of 15 A, which satisfies the required pulse duration and 70 % of the beam current for JT-60SA. R&D progress of accelerator design for the voltage holding capability and the grid power loading improved the pulse duration with high power density of 185 MW/m (974 keV, 190 A/m) from 0.4 s to 60 s, which has reached the ITER requirement level for power density of 200 MW/m. The total power loading on the acceleration grids was less than 13 % of the input power for the 60 s accelerated beams, which is less than the ITER accelerator design of 20 %.