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Numerical Study of Spectral Line Shapes in High-Density He Plasmas

Hayato KAWAZOME and Shinichi NAMBA¹⁾

Department of Information Engineering, National Institute of Technology, Kagawa College, 551 Kohda, Takuma-cho, Mitoyo 769-1192, Japan

1)

Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashihirosima 739-8527, Japan

(Received 30 November 2015 / Accepted 18 October 2016 / Published 9 December 2016)

Abstract

In order to determine the densities and temperatures in high-density helium plasmas by emission spectroscopy, a numerical study of He I spectral line shapes have been performed taking into account radiation trapping. A computational simulation code has been developed, consisting of two parts. The first part solves coupled rate equations to obtain population densities in each energy level of the He atom. The other describes the absorption rate, emission rate, and spectral line shapes by solving the equation of radiation transfer. In a homogeneous plasma, the calculated line profile has a central dip caused by photoabsorption by residual cold atoms. In addition, the results show that radiation trapping significantly alters the population dynamics. The population densities estimated from the intensity of the line profile considering the photoabsorption are lower by one order of magnitude than those without the photoabsorption. For application to a He arc plasma, the temporal evolution of this central dip is also examined as a preliminary calculation.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

spectral line shape, radiation transfer, coupled rate equations, He arc plasma

DOI: 10.1585/pfr.11.2401124

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