[Table of Contents]

Plasma and Fusion Research

Volume 8, 1402092 (2013)

Regular Articles

Impurity Deposition on a First Mirror Surface during Hydrogen Discharges in LHD
Tsuyoshi AKIYAMA, Naoaki YOSHIDA1), Masayuki TOKITANI, Suguru MASUZAKI, Kazuo KAWAHATA, Shigeki OKAJIMA2) and Kazuya NAKAYAMA2)
National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
1)
Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580, Japan
2)
Chubu University, Matsumoto-cho, Kasugai-shi, Aichi 487-8501, Japan
(Received 28 December 2012 / Accepted 26 April 2013 / Published 19 June 2013)

Abstract

First mirrors in fusion devices have to retain the reflectivity and the degradation mechanism and dominant plasma operations that affect the reflectivity have to be understood. The reflectivity of visible laser light (635 nm) of a corner cube mirror is almost entirely determined by the initial hydrogen glow discharges for wall conditioning before conducting a main plasma experiment in the Large Helical Devices (LHD). The hydrogen glow discharge forms a carbon deposition layer on the mirror surface, which degrades its reflectivity. A neon glow discharge and subsequent main discharges had less effect.

Keywords

first mirror, impurity deposition, SEM, GD-OES

DOI: 10.1585/pfr.8.1402092

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This paper may be cited as follows:

Tsuyoshi AKIYAMA, Naoaki YOSHIDA, Masayuki TOKITANI, Suguru MASUZAKI, Kazuo KAWAHATA, Shigeki OKAJIMA and Kazuya NAKAYAMA, Plasma Fusion Res. 8, 1402092 (2013).