| Co-Investigator(Kenkyū-buntansha) |
HARIADA Kazuaki Kyushu University, Research Institute for Applied Mechanics, Prof., 応用力学研究所, 教授 (30222219)
ZUSHI Hideki Kyushu University, Research Institute for Applied Mechanics, Prof., 応用力学研究所, 教授 (20127096)
NAKAMURA Kazuo Kyushu University, Research Institute for Applied Mechanics, Prof., 応用力学研究所, 教授 (30117189)
HASEGAWA Makoto Kyushu University, Research Institute for Applied Mechanics, Research Assoc., 応用力学研究所, 助手 (00325482)
JOTAKI Eriko Kyushu University, Research Institute for Applied Mechanics, Assoc. Prof., 応用力学研究所, 助教授 (40211297)
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| Research Abstract |
Longtime steady-state operation is a critical issue for future fusion devices. In long duration discharges, phenomena with a long 'time-constant appear, although those cannot be seen in short pulse discharges. A phenomenon of "wall saturation and refreshment" is one of those. In order to investigate the. mechanism of the wall saturation and refreshment, we constructed a measurement system of profiles of Hu intensity 'of the plasma and we introduced a Monte-Carlo simulation code. "DEGAS". Moreover, an analysis of a global particle balance during long duration discharges has been carried out in the superconducting tokamak TRIAM-1M.
In a 3-hour discharge on TRIAM-1M, the H_u line intensity spontaneously increased at 〜 30 min and the piezoelectric valve for the fueling was automatically closed by feedback control. A1 1〜30 mm, the global balance between the hydrogen absorption and release, of the wall (i.e., wall saturation) was achieved, and then the plasma density was maintained by the recycling flux alone until the end of the discharge. The measurement result of the toroidal profile of the H_u intensity indicates that the increase in the H_u, intensity (i.e. influx to the, plasma) is caused by the contribution from the whole toroidal area. From the temperature trace of the poloidal limiter and the main chamber, the wall saturation seems to be caused by the increase in hydrogen release from the main chamber due to its temperature increase. It is suggested that the phenomenon of the wall saturation and refreshment depends on the amount of retained hydrogen in the. wall, which depends on the history of the discharges. In the simulation of DEGAS, the. poloidal profile of H_u, intensity can be almost reproduced using a model in which neutral hydrogen particles ire released uniformly from the. whole area of the main chamber surface.
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