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Hydrogen Retention Behavior in Boron Films Affected by Impurities Introduced by Hydrogen Plasma Exposure in the LHD

Katsushi MATSUOKA, Makoto KOBAYASHI, Kiyotaka KAWASAKI, Tetsuo FUJISHIMA, Yuto MIYAHARA, Naoko ASHIKAWA¹⁾, Kiyohiko NISHIMURA¹⁾, Akio SAGARA¹⁾, Yasuhisa OYA and Kenji OKUNO

Radioscience Research Laboratory, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan

1)

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

(Received 30 November 2011 / Accepted 7 November 2012 / Published 26 December 2012)

Abstract

The chemical states of impurities such as oxygen and carbon and their effects on hydrogen retention behavior in pure boron films exposed to hydrogen plasma in the Large Helical Device were investigated by X-ray photoelectron spectroscopy and thermal desorption spectroscopy. The atomic concentrations of the boron films after hydrogen plasma exposure changed from 94% B, 4% C, and 2% O to 68% B, 20% C, and 12% O. B-C bonds and free oxygen were the major chemical states of impurities in the boron films after hydrogen plasma exposure. The hydrogen isotope retention behavior of a hydrogen-plasma-exposed boron film and a D₂⁺-implanted one clearly differed, and the retention of hydrogen as B-H bonds was reduced by hydrogen plasma exposure owing to the chemical sputtering of hydrogen with free oxygen. In addition, the hydrogen desorption stage was observed as B-C-H bonds at approximately 900 K, although the amount of retention as B-C-H bonds was 10% of the total for a pure boron film exposed to hydrogen plasma.

Copyright (c) 2012 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

hydrogen plasma, hydrogen retention, boronization, oxygen, carbon

DOI: 10.1585/pfr.7.2401157

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This paper may be cited as follows:

Katsushi MATSUOKA, Makoto KOBAYASHI, Kiyotaka KAWASAKI, Tetsuo FUJISHIMA, Yuto MIYAHARA, Naoko ASHIKAWA, Kiyohiko NISHIMURA, Akio SAGARA, Yasuhisa OYA and Kenji OKUNO, Plasma Fusion Res. 7, 2401157 (2012).