Production of long pulse negative ion beam by using actively cooled plasma grid

Kojima, Atsushi; Hanada, Masaya; Yoshida, Masafumi; Kashiwagi, Mieko; Tobari, Hiroyuki; Umeda, Naotaka; Watanabe, Kazuhiro; NB Heating Technology Group

In this paper, the recent activities on the new test stand are reported toward demonstration of the long pulse production for 22A, 100s negative ion beams. As for the temperature control of the plasma grid, a prototype of the grid with cooling/heating by circulating a high-temperature fluorinated fluid has been developed. This grid was found to have a capability to control the temperature with a time constant of 10 s by considering the physical properties of the fluid. As a result, 120 A/m beams for 100 s have been achieved, which is about 90 percent of the rated value for JT-60SA.