Author :
Ebisawa, N. ; Akino, N. ; Grisham, L. ; Hanada, M. ; Honda, A. ; Inoue, T. ; Kawai, M. ; Kazawa, M. ; Kikuchi, K. ; Komata, M. ; Mogaki, K. ; Noto, K. ; Okano, F. ; Ohga, T. ; Oshima, K. ; Takenouchi, T. ; Tanai, Y. ; Umeda, N. ; Usui, K. ; Yamazaki, H. ;
Abstract :
The pulse duration of the negative ion based NBI system has been extended from 10 s to 25 s to study long pulse plasmas on JT-60U. A feedback control technique has been demonstrated to keep the arc power constant by controlling the filament voltage for long pulse operation. Thus it was clearly observed that the negative ion beam current increased with the temperature of the plasma grid at constant arc power. A tapered filament is employed to improve its durability for the next operational campaign. Moreover, a high voltage holding test indicates that the reduction in the outgassing from the FRP (fiberglass-reinforced plastic) insulator may be a key to suppress the breakdowns in the ion source
Keywords :
Tokamak devices; fibre reinforced plastics; fusion reactor design; fusion reactor ignition; fusion reactor operation; glass fibre reinforced plastics; ion sources; plasma beam injection heating; plasma sources; plasma temperature; FRP insulator; JT-60U; arc power constant; feedback control technique; fiberglass-reinforced plastic; filament voltage; heat flux; high voltage holding test; ion source; long pulse plasmas; negative ion based NBI system; negative ion beam current; plasma grid; plasma temperature; tapered filament; Breakdown voltage; Feedback control; Fiber reinforced plastics; Insulator testing; Ion beams; Optical fiber testing; Plasma sources; Plasma temperature; Plastic insulation; Voltage control; FRP; JT-60U; NBI; feedback control; filament; negative ion; voltage holding;
