Plasma and Fusion Research

Volume 2, 014 (2007)

Regular Articles

High-Resolution VUV Spectra of Carbon, Neon and Argon in a Wavelength Range of 250 to 2300 Å for Plasma Diagnostics Observed with a 3 m Normal Incidence Spectrometer in LHD

Ryuji KATAI, Shigeru MORITA¹⁾ and Motoshi GOTO¹⁾

Department of Fusion Science, The Graduate University for Advanced Studies
1): National Institute for Fusion Science

(Received 9 January 2007 / Accepted 4 March 2007 / Published 9 May 2007)

Abstract

Intrinsic impurities have been much reduced in toroidal fusion devices through the development of several wall-conditioning techniques as well as by the use of carbon materials in the first wall and divertor plates. Impurity elements useful for passive plasma spectroscopy have been then extremely limited. At present, only carbon is a subject for spectroscopic diagnostics in most discharges except for fuel atoms. The use of rare gas as a brighter light source is a method to overcome the present difficulty in passive spectroscopy. Recently, rare gases have also been used for edge cooling to reduce the divertor heat flux. Therefore, high-resolution spectra (Δλ ∼ 0.2 Å) from neon and argon in a 250 to 2300 Å wavelength range have been measured using a 3 m normal incidence spectrometer in Large Helical Device (LHD) and the measured spectra were precisely analyzed. The VUV spectra of carbon, neon and argon are presented for spectroscopic use and their wavelengths are tabulated with their relative intensities. The spectral profiles of almost all the spectral lines measured here are formed by the Doppler broadening and self-absorption processes. The Doppler broadening of neon and argon spectra are plotted against the ionization energies and Doppler spectra from carbon lines are presented. The self-absorption spectra of the hydrogen Lyman-α line, which are found in the LHD high-density discharge, are also presented and the neutral density is analytically estimated.

Keywords

VUV spectrum, carbon, neon, argon, Doppler broadening, self-absorption spectrum, Lyman series

DOI: 10.1585/pfr.2.014

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This paper may be cited as follows:

Ryuji KATAI, Shigeru MORITA and Motoshi GOTO, Plasma Fusion Res. 2, 014 (2007).