Plasma and Fusion Research

Volume 17, 2405041 (2022)

Regular Articles


Measurement of the Bidirectional Reflectance Distribution Function of Tungsten Surface Sputtered in Argon Plasma
Hiroki NATSUME, Kunpei NOJIRI1), Shin KAJITA2), Tomohiko USHIKI1), Tatsuo SUGIE3), Sin-iti KITAZAWA1), Takanori KIKUCHI1), Tomohiro YOKOZUKA1), Hirohiko TANAKA, Noriyasu OHNO and Takaki HATAE1)
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
1)
Naka Fusion Institute, National Institutes for Quantum Science and Technology (QST), Naka 311-0193, Japan
2)
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8603, Japan
3)
Nippon Advanced Technology Co., Ltd., Tokai, Naka District 319-1112, Japan
(Received 23 December 2021 / Accepted 10 March 2022 / Published 13 May 2022)

Abstract

For ITER spectroscopic measurements, it is important to understand the optical reflection characteristics of the divertor surface for an accurate measurement because the stray light in the divertor may be large. We set up a goniophotometer that measures the optical reflection characteristics and investigated the bidirectional reflectance distribution function of tungsten samples sputtered in an argon plasma. The specimens sputtered at temperatures lower than the recrystallization temperature of tungsten exhibited smooth surfaces and strong specular reflections in their optical reflectance characteristics. Recrystallized crystals likely grew for the specimens sputtered at temperatures approximately equal to the recrystallization temperature, resulting in a weak specular reflection.


Keywords

bidirectional reflectance distribution function, goniophotometer, sputtering, spectroscopic diagnostics

DOI: 10.1585/pfr.17.2405041


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