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Author(s):
N. Noda, A. Sagara, H. Yamada, Y. Kubota, N. Inoue, K. Akaishi, O. Motojima, K. Iwamoto, M. Hashiba, I. Fujita, T. Hino, T. Yamashina, K. Okazaki, J. Rice, M. Yamage, H. Toyoda and H. Sugai
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Title:
Boronization Study for Application to Large Helical Device
Date of publication:
July 1994
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Key words:
boronization, wall conditioning, decaborane, in-situ AES, LHD, oxygen capacity, oxygen gettering
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Abstract:
An experimental device named SUT (SUrface modification Teststand) was constructed for a boronization study. An ultra high vacuum (UHV) condition, a changeable high temperature liner and in-situ AES are three distinctive feature of the SUT device. Saturation density of oxygen atoms was as large as 1.2 x 10^17 /cm2 on a boronized surface, whereas 1.5 x 10^16/cm2 on a bare stainless steel surface. It is found by AES analysis that the oxygen-contained layer was as thick as 50 nm from the top surface of the boron film. From such a large oxygen-saturation density, we expect that the oxygen-gettering ability of the boronized surface is likely to be maintained during one-day experiment of LHD. The oxygen -saturation behavior was quite similar between the boronized surfaces obtained with decaborane and diborane, which indicates that, as a working gas of the boronization, the decaborane works well compared with diborane, as afar as oxygen gettering is concerned.
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