Investigation about The mechanism of wall saturation and refreshment in long time plasma-wall interaction

长期稳定运行是未来核聚变装置的关键问题。在长脉冲放电中，出现了长时间常数的现象，而在短脉冲放电中则看不到。“墙壁饱和和刷新”现象就是其中之一。为了调查。在此基础上，构建了等离子体胡强度剖面测量系统，并介绍了Monte-Carlo仿真程序。“德”。此外，还在超导托卡马克TRIAM-1M中进行了长时间放电过程中粒子整体平衡的分析。在TRIAM-1M上放电3小时，H_u线强度在~ 30 min自发增加，并通过反馈控制自动关闭加氢压电阀。A1 1 ~ 30mm时，壁面吸氢和释氢达到全局平衡（即壁面饱和），然后仅靠循环通量维持等离子体密度，直至放电结束。H_u强度环面剖面的测量结果表明，H_u强度的增加（即流入等离子体）是由整个环面面积的贡献引起的。从极向限制器和主室的温度迹线来看，壁面饱和似乎是由于主室温度升高导致氢气释放量增加所致。认为壁面的饱和和刷新现象取决于壁面中保留氢的量。这取决于排放的历史。在DEGAS的仿真中，用中性氢粒子均匀地从等离子体中释放出来的模型，几乎可以再现H_u的极向分布。主室表面的整个区域。

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.