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Application of He I Line Intensity Ratio Method to Tokamak Plasma in TOKASTAR-2

Ryoma YOKOYAMA, Atsushi OKAMOTO, Takaaki FUJITA, Hideki ARIMOTO, Masato MINOURA, Kohei YASUDA and Takahiro YAMAUCHI

Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan

(Received 28 December 2017 / Accepted 19 March 2018 / Published 22 May 2018)

Abstract

Temporal evolution of electron density and temperature in TOKASTAR-2 tokamak plasma is obtained for the first time by He I line intensity ratio method. In the calculation of collisional radiative model, we consider the effect of radiation trapping and validity of quasi-steady-state approximation for metastable states. He I line intensities are measured using a monochromator that has a photomultiplier tube as a detector. To evaluate line intensity ratios used for analysis, their sensitivity factors for plasma parameters are newly introduced. We investigate plasma current I_p dependence of the electron density n_e and temperature T_e by changing the charging voltage of ohmic heating V_OH. The n_e depended on I_p independent of V_OH. The Spitzer resistance obtained from the measured T_e was consistent with the plasma resistance at I_p top phase.

Copyright (c) 2018 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

TOKASTAR-2, He I line intensity ratio method, CR model, radiation trapping, tokamak plasma

DOI: 10.1585/pfr.13.3402047

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