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Initial phase wall conditioning in KSTAR

2011; IOP Publishing; Volume: 51; Issue: 10 Linguagem: Inglês

10.1088/0029-5515/51/10/103027

1741-4326

Suk–Ho Hong, Kwang Pyo Kim, Sung Woo Kim, Jong-Ho Sun, Dong-Su Lee, Hyun-Jong Woo, Sang‐Yong Tom Lee, Sang-Hwa Lee, Eunkyung Park, Sang‐Joon Park, Kyung-Min Kim, KunSu Lee, Sun-Ho Kim, Jongsu Kim, Sun-Jung Wang, Jaemin Park, Woong-Chae Kim, Hak-Kun Kim, Kaprai Park, Hyung-Lyeol Yang, Y.K. Oh, J.G. Kwak, Hoon-Kyun Na, Jaeyong Kim, Kyu‐Sun Chung,

Particle accelerators and beam dynamics

The initial phase wall conditioning in KSTAR is depicted. The KSTAR wall conditioning procedure consists of vessel baking, glow discharge cleaning (GDC), ICRH wall conditioning (ICWC) and boronization (Bz). Vessel baking is performed for the initial vacuum conditioning in order to remove various kinds of impurities including H 2 O, carbon and oxygen and for the plasma operation. The total outgassing rates after vessel baking in three successive KSTAR campaigns are compared. GDC is regularly performed as a standard wall cleaning procedure. Another cleaning technique is ICWC, which is useful for inter-shot wall conditioning under a strong magnetic field. In order to optimize the operation time and removal efficiency of ICWC, a parameter scan is performed. Bz is a standard technique to remove oxygen impurity from a vacuum vessel. KSTAR has used carborane powder which is a non-toxic boron-containing material. The KSTAR Bz has been successfully performed through two campaigns: water and oxygen levels in the vacuum vessel are reduced significantly. As a result, KSTAR has achieved its first L–H mode transition, although the input power was marginal for the L–H transition threshold. The characteristics of boron-containing thin films deposited for boronization are investigated.