Plasma and Fusion Research

Volume 7, 2405121 (2012)

Regular Articles

Fatal Damages due to Breakdown on a Diagnostic Mirror Located outside the Vacuum Vessel in JT-60U
Shin KAJITA, Takaki HATAE1), Takeshi SAKUMA1), Shuichi TAKAMURA2), Noriyasu OHNO3) and Kiyoshi ITAMI1)
EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan
1)
Japan Atomic Energy Agency, Ibaraki 311-0193, Japan
2)
Aichi Institute of Technology, Toyota 470-0392, Japan
3)
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
(Received 23 November 2011 / Accepted 29 June 2012 / Published 13 September 2012)

Abstract

Some discharge phenomena seriously damaged the secondary mirror for Thomson scattering diagnostics, which was located outside the vacuum vessel. In this paper, the surface damages recorded on the mirror are observed in detail with an optical microscope. Many fine trails were found on the surface. The trails could be categorized into two different types with respect to the trail width. The mechanisms to lead the damages were discussed based on the observation. This study issues warning on the components to be installed in future fusion devices both inside and outside the vacuum vessel.

Keywords

diagnostic mirror, breakdown, arcing, surface discharge

DOI: 10.1585/pfr.7.2405121

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This paper may be cited as follows:

Shin KAJITA, Takaki HATAE, Takeshi SAKUMA, Shuichi TAKAMURA, Noriyasu OHNO and Kiyoshi ITAMI, Plasma Fusion Res. 7, 2405121 (2012).