Plasma and Fusion Research

Volume 12, 1302048 (2017)

Letters


Effects of Mild Baking on Hydrogen Removal from the Modified Surface of the First Wall in the LHD
Yuji NOBUTA, Suguru MASUZAKI1), Masayuki TOKITANI1), Naoko ASHIKAWA1) and LHD Experimental Group1)
Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
1)
National Institute for Fusion Science, Oroshi-cho, Toki 509-5292, Japan
(Received 23 May 2017 / Accepted 6 November 2017 / Published 28 November 2017)

Abstract

An additional deuterium irradiation was performed for long-term samples mounted on the first wall in the large helical device (LHD) to investigate the effect of mild baking (at 368 K) on fuel hydrogen removal from the modified surface. The efficiency of baking strongly depended on the surface conditions. In the erosion dominant area, almost all the retained deuterium was removed by baking, whereas only 17% and 13% of the retained deuterium were removed from the boron and carbon deposition areas, respectively. The results suggest that the erosion dominant area in the first wall can act as a pumping wall during the main discharge, and, in contrast, the fuel hydrogen retention can continuously increase in boron and carbon deposition areas owing to the low removal efficiency of fuel hydrogen given that the deposition continues during the plasma discharge.


Keywords

baking, desorption, retention, surface modification, deposition, deuterium irradiation

DOI: 10.1585/pfr.12.1302048


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