Investigation of the silicon coated film characteristics on tungsten surface in EAST fusion device

• Published in: Nuclear materials and energy 2023-03, Vol.34 (C), p.101368, Article 101368
• Main Authors: Guan, Yanhong, Zuo, Guizhong, Meng, Xiancai, Xu, Wei, Yu, Yaowei, Huang, Ming, Li, Lin, Hu, Jiansheng
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EAST; Nuclear Science & Technology; Plasma; Siliconization; Tungsten
• ISSN: 2352-1791; 2352-1791
• DOI: 10.1016/j.nme.2023.101368

•Siliconization using 10 % SiD4 + 90 % He assisted by ICRF or GD are performed to improve plasma confinement performance on EAST device with full W wall.•Higher baking temperature of the W sample is beneficial for obtaining the more compact and smoother Si film.•Enhanced ICRF working power from 20 kW to 40 kW could further increase the ratio of Si/O and increase the thickness of the Si film.•Siliconization assisted by GD is more uniform and thicker, and the ratio of Si/O is effectively improved. Siliconization using 10 % SiD4 + 90 % He assisted by ion cyclotron range of frequency discharge (ICRF) or glow discharge (GD) was performed in EAST with full tungsten (W) diverters. It was found that the coated Si film on W sample at a higher baking temperature (160 °C) was smoother than that at a lower baking temperature (60 °C). This was mainly because physically adsorbed gaseous impurities were released at a higher baker temperature. This process improved the adhesion between the film and the surface of W. An increase in the ICRF working power from 20 kW to 40 kW further increased the Si content and the film thickness by 1.5 times. The cleaning efficiency of ICRF on the surface of the W sample before siliconization was higher at 40 kW than that at 20 kW, which facilitated the removal of oxides and other compounds from the surface of W. The ratio of silicon/oxygen (Si/O) and the thickness improved considerably due to greater ionization and deposition of SiD4. Additionally, siliconization via GD was more uniform and 1.5 nm thicker than that via ICRF, which was because of the greater working gas pressure, coating duration, and homogeneity in GD. These results might be used as a reference for evaluating the effect of siliconization on plasma performance and its application in fusion devices.