Simultaneous Observation of Tungsten Spectra of W0 to W46+ Ions in Visible, VUV and EUV Wavelength Ranges in the Large Helical Device

Abstract

Spectroscopic studies for emissions released from tungsten ions have been conducted in the Large Helical Device (LHD) for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. Tungsten ions are distributed in the LHD plasma by injecting a pellet consisting of a small piece of tungsten metal wire enclosed by a carbon tube. Line emissions from W0, W5+, W6+, W24+–W28+, W37+, W38+, and W41+–W46+ are observed simultaneously in the visible (3200–3550 Å), vacuum ultraviolet (250–1050 Å), and extreme ultraviolet (5–300 Å) wavelength ranges and the wavelengths are summarized. Temporal evolutions of line emissions from these charge states are compared for comprehensive understanding of tungsten impurity behavior in a single discharge. The charge distribution of tungsten ions strongly depends on the electron temperature. Measurements of emissions from W10+ to W20+ are still insufficient, which is addressed as a future task.

Detailed Analysis of Spectra from Ga-like Ions of Heavy Elements Observed in High-Temperature Plasmas

“…Though the measured wavelengths for Z less than 63 are missing because of the limited wavelength range of the spectrometers used in this study, the calculated wavelength is given in the entire range of Z. We took the measured wavelength for tungsten (Z = 74) from our previous paper [2]. Though the wavelength of the M1 line for ytterbium (Z = 70) has also been reported recently in NIST EBIT [14], the M1 lines for the other elements (Z = 63-69 and 71) have been identified experimentally for the first time in this study.…”

“…Extreme ultraviolet (EUV) and soft X-ray emission spectra from highly charged heavy ions are of great interest in a variety of research fields such as nuclear fusion [1,2], industrial light source applications [3,4], and basic atomic physics [5,6]. Among a wide range of ion stages of highly charged heavy ions, gallium-like (Ga-like) ions have a relatively simple ground state configuration, [Ar]3d 10 4s 2 4p, which includes only three N-shell electrons outside the closed M-shell.…”

EUV spectral shape variation of tungsten unresolved transition arrays in electron temperature range of 2–4 keV observed in the Large Helical Device

“…In these cases, characteristic tungsten spectra are observed even during the latter half of the discharge with the low electron temperature below 1 keV, and the spectral shape is summarized in Ref. [4]. When Te0 was around 2 keV, W 24+ -W 33+ and W 27+ -W 29+ UTAs were observed at 20-33 Å and 48-55 Å, respectively.…”

“…Tungsten ions are distributed in the LHD plasma by injecting a pellet consisting of a small piece of tungsten metal wire enclosed by a carbon tube. Emission lines of tungsten ions from W 0 -W 46+ have been observed via extreme ultraviolet (EUV), vacuum ultraviolet (VUV), and visible spectroscopy [4][5][6]. In this paper, the tungsten UTA spectra observed using two flat-field EUV spectrometers in the wavelength ranges 6-60 Å and 130-340 Å are presented.…”

EUV/VUV Spectroscopy for the Study of Carbon Impurity Transport in Hydrogen and Deuterium Plasmas in the Edge Stochastic Magnetic Field Layer of Large Helical Device

“…This measurement technique enables simultaneous coverage of a wide wavelength range from EUV to VUV. It has been applied to survey the emission spectra of various impurities, including neon injected by gas puffing [18], boron and nitrogen injected by powder dropping [19], and tungsten injected as pellets [20].…”