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内容記述 |
The JT-60SA project is in progressing to explore new domain in the high beta plasmas complementing ITER toward DEMO, and the first plasma generation was achieved in 2023. The vacuum must have been cleaned before attempting tokamak discharges, therefore, wall conditioning was performed by 200°C baking and discharge cleaning.In the JT-60SA, the vacuum vessel (VV) is evacuated by a total of eight turbo molecular pumps through the two manifolds, which equipped with vacuum gauges and a residual gas analyzer (RGA) to monitor the total pressure and gas species in the VV. Three glow discharge cleaning (GDC) electrodes were equipped in the toroidal direction. The impurities on the wall were removed by DC glow discharge generated with vacuum vessel (VV) as a cathode. The pressure in the VV was increased to generate a glow discharge, so that the gas was continuously injected while being evacuated by a single turbo molecular pump. To facilitate the ignition of the glow discharge, electrons were emitted from the pre-ionizing electrode before the glow discharge was ignited. GDC during 200°C baking was performed in July 2023 and GDC during 50°C baking was performed in August 2023. As a result of GDC during 200°C baking, impurity gas release was measured by RGA, and reduction of impurities such as M/Z=18, 36 was confirmed with various data measured. On the other hand, almost no impurity release was observed in GDC during 50°C baking compared to the GDC during baking at 200°C. The details of the reduction of each impurity by GDC will be reported. |
