[Table of Contents]

Plasma and Fusion Research

Volume 8, 2402176 (2013)

Regular Articles

Two-Dimensional Distribution of Electron Temperature in Ergodic Layer of LHD Measured from Line Intensity Ratio of CIV and NeVIII
Erhui WANG1), Shigeru MORITA1,2), Chunfeng DONG2), Motoshi GOTO1,2), Izumi MURAKAMI1,2) and Tetsutarou OISHI1,2)
1)
Department of Fusion Science, Graduate University for Advanced Studies, Toki, Gifu 509-5292, Japan
2)
National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
(Received 30 November 2012 / Accepted 18 November 2013 / Published 27 December 2013)

Abstract

Two-dimensional distribution of impurity lines emitted from ergodic layer with stochastic magnetic field lines in Large Helical Device (LHD) has been observed using a space-resolved extreme ultraviolet (EUV) spectrometer. The two-dimensional electron temperature distribution in the ergodic layer is successfully measured using the line intensity ratio of Li-like NeVIII 2s-3p (2S1/2-2P3/2: 88.09 Å, 2S1/2-2P1/2: 88.13 Å) to 2p-3s (2P1/2-2S1/2: 102.91 Å, 2P3/2-2S1/2: 103.09 Å) transitions emitted from radial location near Last Closed Flux Surface (LCFS). The intensity ratio analyzed with ADAS code shows no dependence on the electron density below 1014 cm−3. The result indicates a little higher temperature, i.e., 220 eV, in the poloidal location at high-field side near helical coils called O-point compared to the temperature near X-point, i.e., 170 eV. The electron temperature profile is also measured at the edge boundary of ergodic layer using the line intensity ratio of Li-like CIV 2p-3d (2P1/2-2D3/2: 384.03 Å, 2P3/2-2D5/2: 384.18 Å) to 2p-3s (2P1/2-2S1/2: 419.53 Å, 2P3/2-2S1/2: 419.71 Å) transitions. The intensity ratios analyzed with CHIANTI, ADAS and T.Kawachi codes show a slightly higher temperature near O-point, i.e., 25 eV for CHIANTI, 21 eV for ADAS and 11 eV for T.Kawachi's codes, compared to the temperature at X-point, i.e., 15 - 21 eV for CHIANTI, 9 - 15 eV for ADAS and 6 - 9 eV for T.Kawachi codes. It suggests that the transport coefficient in the ergodic layer is varied with three-dimensional structure.

Keywords

line intensity ratio, electron temperature, Li-like CIV and NeVIII, EUV spectrometer

DOI: 10.1585/pfr.8.2402176

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This paper may be cited as follows:

Erhui WANG, Shigeru MORITA, Chunfeng DONG, Motoshi GOTO, Izumi MURAKAMI and Tetsutarou OISHI, Plasma Fusion Res. 8, 2402176 (2013).