Hydrogen removal by electron cyclotron wall conditioning with neon gas and its impact of tokamak plasma start-up on the QUEST spherical tokamak

• DOI: 10.1088/1741-4326/ad3d6e
• Publication Date: 2024-04-11T22:22:46Z
• Authors: Masakatsu Fukumoto; Qilin Yue; Kazuaki Hanada; Shinichiro Kojima; Tomohide Nakano; Naoaki Yoshida; Ryuya Ikezoe; Yoshihiko Nagashima; Takeshi Ido; Takumi Onchi; Hiroshi Idei; Hiroki Iguchi; Takumi Komiyama; Taiichi Shikama; Akira Ejiri; Suguru Masuzaki; Mizuki Sakamoto; Yoshio Ueda; Kengoh Kuroda; Kaori Kono; Shun Shimabukuro; Aki Higashijima
• Keywords: QUEST; Nuclear and particle physics. Atomic energy. Radioactivity; 0103 physical sciences; neon; QC770-798; hydrogen removal; electron cyclotron wall conditioning; 01 natural sciences

Abstract Electron cyclotron wall conditioning with neon gas (Ne-ECWC) has been performed on the normal conducting spherial tokamak QUEST with metal walls under a trapped particle configuration with O-mode EC waves including X-mode polarization with a frequency of 8.2 GHz and an injection power of 16 kW. The Ne-ECWC removes hydrogen from the wall with small neon retention. The Ne-ECWC decreases hydrogen recycling at the following tokamak discharges, contributing to an improvement of the following tokamak plasma start-up: the plasma current increases and the start-up timing of the plasma current shifts forward. However, defects such as voids and bubbles are formed on tungsten surface exposed to the Ne-ECWC plasma.