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Evaluation of Plasma-Wall Interactions Using Material Probes in the Large Helical Device

Takuya SHIGEMURA, Naoyuki SHINODA, Yuji YAMAUCHI¹⁾, Yuji NOBUTA¹⁾, Tomoaki HINO¹⁾, Naoko ASHIKAWA²⁾, Akio SAGARA²⁾, Kiyohiko NISHIMURA²⁾ and LHD Experimental Group²⁾

Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Japan

1)

Faculty of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Japan

2)

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

(Received 22 November 2012 / Accepted 30 September 2013 / Published 15 November 2013)

Abstract

Control of plasma-wall interactions (PWIs) and understanding their mechanism are essential issues for realization of fusion reactor. In this study, plasma-wall interactions during FY2010 and FY2011 experiments in the Large Helical Device (LHD) were analyzed by using material probes. We installed material probes at the positions expected to have different deposits of materials such as boron and titanium and investigated the correlation between this impurity deposition and gas retention. The desorption behavior of hydrogen and helium depended on the level of impurity deposition. We observed a new peak for hydrogen desorption at the probe with large boron deposits. The amount of retained hydrogen was large in that probe; however the amount of retained helium was small in the same probe, which is opposite what we observe in the probe with titanium deposits and the probe with a thin deposition layer.

Copyright (c) 2013 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

material probe, plasma wall interactions, Large Helical Device, boronization, helical system

DOI: 10.1585/pfr.8.2405162

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This paper may be cited as follows:

Takuya SHIGEMURA, Naoyuki SHINODA, Yuji YAMAUCHI, Yuji NOBUTA, Tomoaki HINO, Naoko ASHIKAWA, Akio SAGARA, Kiyohiko NISHIMURA and LHD Experimental Group, Plasma Fusion Res. 8, 2405162 (2013).