Visible emission spectroscopy of highly charged tungsten ions in LHD: II. Evaluation of tungsten ion temperature

TL;DR

This study used polarization-resolved high-resolution spectroscopy to evaluate the temperature of highly charged tungsten ions in LHD plasma, revealing that their temperature is comparable to helium-like argon ion temperature.

Contribution

First-time evaluation of tungsten ion temperature in LHD plasma using spectral line broadening and Abel inversion techniques.

Findings

W tungsten ion temperature is similar to helium-like argon ion temperature.

Spectral broadening attributed to Doppler effects.

Polarization dependence linked to Zeeman splitting.

Abstract

We demonstrated a polarization-resolved high resolution spectroscopy of a visible emission line of highly charged tungsten ions ({\lambda}0 = 668.899 nm, Shinohara et al Phys. Scr. 90 125402) for the large helical device (LHD) plasma, where the tungsten ions were introduced by a pellet injection. Its spectral profile shows broadening and polarization dependence, which are attributed to the Doppler and Zeeman effects, respectively. The tungsten ion temperature was evaluated for the first time from the broadening of visible the emission line, with its emission location determined by the Abel inversion of the chord-integrated emission intensities observed with multiple chords. The tungsten ion temperature was found to be close to the helium-like argon ion temperature, which is used as an ion temperature monitor in LHD