[Table of Contents]

Plasma and Fusion Research

Volume 7, 2402059 (2012)

Regular Articles

Vertical Profiles and Radial Locations of He II and C IV Line Emissions Observed at Different Toroidal Angles in LHD
Erhui WANG1), Shigeru MORITA1,2), Motoshi GOTO1,2), Masahiro KOBAYASHI1,2) and Chunfeng DONG2)
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 9 December 2011 / Accepted 2 April 2012 / Published 07 June 2012)

Abstract

Vertical profiles of edge impurity line emissions of He II and C IV have been measured at different toroidal locations of Large Helical Device (LHD) by scanning horizontally a space-resolved EUV spectrometer in order to observe the edge distribution at different poloidal locations. Radial location of He II with ionization energy of Ei = 54.4 eV reflects the penetration depth of neutral helium and radial location of C IV with Ei = 64.5 eV expresses the index of plasma edge boundary in ergodic layer of LHD. The result indicates that the radial position of He II is located at inner side than that of C IV, whereas the ionization energy of He II is smaller than that of C IV. It is found that the radial position of He II estimated from the C IV position has a nearly constant distance of 4 mm from the plasma edge against different poloidal locations including region near X-points. The distance is in a good agreement with analysis assumed neutral helium influx with room temperature (300 K). It suggests that the neutral helium mainly enter the plasma as background gas in the vacuum vessel, but not as recycling particle.

Keywords

helium neutral, EUV spectrometer, plasma boundary

DOI: 10.1585/pfr.7.2402059

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This paper may be cited as follows:

Erhui WANG, Shigeru MORITA, Motoshi GOTO, Masahiro KOBAYASHI and Chunfeng DONG, Plasma Fusion Res. 7, 2402059 (2012).