Plasma and Fusion Research

Volume 16, 1202094 (2021)

Rapid Communications

Simultaneous Observation of Silicon and Boron Impurity Behaviors in the Core Region of a Mid-Density LHD Plasma
Naoki TAMURA1,2), Mikirou YOSHINUMA1), Katsumi IDA1,2), Chihiro SUZUKI1,2), Motoshi GOTO1,2), Tetsutarou OISHI1,2), Mamoru SHOJI1), Kiyofumi MUKAI1,2) and Hisamichi FUNABA1)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
2)
The Graduate University for Advanced Studies, SOKENDAI, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
(Received 2 July 2021 / Accepted 18 July 2021 / Published 7 September 2021)

Abstract

Line emissions from both silicon (Si) and boron (B) impurity ions introduced by a single tracer-encapsulated solid pellet (TESPEL) containing silicon hexaboride (SiB6) powders were successfully observed using the extreme ultraviolet (EUV) spectrometer and charge-exchange spectroscopy (CXS) technique in the Large Helical Device. The CXS diagnostic shows clearly that a hollow radial profile of fully ionized B impurities was created immediately after the TESPEL injection, and such a hollow profile was relaxed with time. At the same time, Li-like emissions from the highly ionized Si impurities were also observed with the EUV spectrometer, SOXMOS. Therefore, the decay times of these impurities could be estimated under the same plasma conditions. The estimated decay time of the Si impurities, τSi = 0.12 ± 0.01 s, was found to be slightly longer than that of the B impurities, τB = 0.09 ± 0.01 s

Keywords

TESPEL, impurity transport, neoclassical transport, turbulent transport, Z-dependence

DOI: 10.1585/pfr.16.1202094

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