1. Long Pulse Operation on NBI Systems for JT-60U
- Author
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N. Ebisawa, K. Usui, N. Akino, Y. Ikeda, T. Ohga, K. Mogaki, T. Yamamoto, M. Kazawa, Mikito Kawai, L. Grisham, N. Umeda, and A. Honda
- Subjects
Nuclear and High Energy Physics ,Materials science ,020209 energy ,Mechanical Engineering ,Magnetic confinement fusion ,Pulse duration ,02 engineering and technology ,Plasma ,01 natural sciences ,Neutral beam injection ,Ion source ,010305 fluids & plasmas ,Nuclear Energy and Engineering ,Ionization ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Limiter ,General Materials Science ,Duct (flow) ,Atomic physics ,Civil and Structural Engineering - Abstract
In the neutral beam injection (NBI) system, an extension of the pulse duration up to 30 sec has been intended to study quasi-steady state plasma on JT-60U. The four positive-ion based (P-NBI) units, which tangentially inject neutral beam to plasma, were mainly modified on the electric power supplies and the beam limiters to extend the pulse duration up to 30 sec with 2 MW at 80 keV per each. The seven P-NBI units, each of which perpendicularly injects for 10 sec, were conducted to operate in series for the total pulse duration of 30 sec. The ion source of the negative-ion based (N-NBI) unit, whose target beam energy is 500 keV for 10 sec, was also modified to reduce the heat load of the grid for long pulse operation. The reduction of the re-ionization of the neutral beam in the beam drift duct was a key to achieve a long pulse injection. It was found that the pressure rise in the beam drift duct, which gives the re-ionization rate, depended on the temperature of the re-ionization plates during NBI injection. Up to now, it was attained successfully that the pulse duration of the tangential P-NBI unit was extended up tomore » 30 sec. 310 MJ of the total integrated injection energy into JT-60U plasma was achieved, including the negative-ion based NBI operation for 17 sec at 366 keV.« less
- Published
- 2005