Tungsten spectroscopy relevant to the diagnostics of ITER divertor plasmas

Abstract

The possibility of using extreme ultraviolet emission from low charge states of tungsten ions to diagnose the divertor plasmas of the ITER tokamak has been investigated. Spectral modelling of Lu-like W 3+ to Gd-like W 10+ has been performed by using the Flexible Atomic Code, and spectroscopic measurements have been conducted at the Sustained Spheromak Physics Experiment (SSPX) in Livermore. To simulate ITER divertor plasmas, tungsten was introduced into the SSPX spheromak by prefilling it with tungsten hexacarbonyl prior to the usual hydrogen gas injection and initiation of the plasma discharge. The tungsten emission was studied using a grazing-incidence spectrometer.

Energy levels and radiative data for Kr-like W38+from MCDHF and RMBPT calculations

“…The lowest four states belong to the 3 2 , 3 2 term and are all lowered about −4000 cm −1 by the Breit interaction and −1500 cm −1 by the self-energy. For the next term - 3 2 , 5 2 the corresponding numbers are about −7500 and −1200 cm −1 . Finally, the two highest terms -1 2 , 5 2 and 1 2 , 3 2 are lowered by about −12000 and −15000 cm −1 by the Breit and −700 and −500 cm −1 by QED, respectively.…”

Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics

“…At lower energies, the emission consists of isolated spectral lines, whereas at higher energies, the spectra are made up of emission bands with only a smaller number of identifiable lines. The analysis is therefore focused on the low-energy emission, which, based on previous spectral modeling calculations [18], is believed to originate from Yb-like W V, Tm-like W VI, Er-like W VII and Ho-like W VIII. The evolution of emission with electron-beam energy together with ab initio wavelength calculations was utilized to interpret the low-energy survey and high-resolution spectra.…”

“…Emission from low charge states of tungsten has been observed in magnetic fusion plasmas, however, not with enough resolution to allow for detailed spectroscopic measurements. The Ho-like W VIII spectrum was observed by Veres et al in the MT-1M tokamak [17], and Clementson et al recorded spectra of Tm-like through Ho-like W VI-VIII at the SSPX spheromak [18]. However, without additional laboratory or theoretical reference data, such plasma spectroscopic measurements are difficult to interpret.…”

Quasirelativistic calculation of 4s24p5, 4s24p44d and 4s4p6configuration spectroscopic parameters for the W39+ion

“…Only reliable theoretical data of the multicharged tungsten ion spectral properties enable to model such types of plasma providing means to its diagnostics, see e.g. [3]. On the other hand, the theoretical energy spectra and transition parameter calculations are helpful in identifying the emission lines of the multicharged tungsten ions which are observed in the specially designed experiments.…”