Impurity and particle recycling reduction by boronization in JT-60U

• Published in: Journal of nuclear materials 1995-04, Vol.220 (1-3), p.375-379
• Main Authors: Higashijima, S., Sugie, T., Kubo, H., Tsuji, S., Shimada, M., Asakura, N., Hosogane, N., Kawano, Y., Nakamura, H., Itami, K., Sakasai, A., Shimizu, K., Ando, T., Saidoh, M.
• Format: Article
• Language: English
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/0022-3115(94)00635-0

In JT-60U boronization using decaborane was carried out. Boronization reduced the oxygen impurity in OH discharges and shortened the wall conditioning after the vacuum vessel vent and consequently enabled JT-60U to produce clean plasmas easily except for NB heated plasmas. After boronization, particle recycling was reduced drastically in OH and NB discharges. High confinement plasmas were obtained including high β p mode and H-mode discharges. In the latest boronization part of divertor plates were replaced with B 4C coated tiles with a B 4C thickness ∼ 300 μm. After introducing B 4C divertor tiles, an explosive generation of boron particles from the tiles was observed. By the combined effects of boronization with decaborane and boron generation from B 4C tiles, oxygen impurity was so low that oxygen line signals were reduced to noise levels after the latest boronization. On the other hand, boron burst from the B 4C tiles restricted the operation of JT-60U.