Quantitative analysis on tungsten spectra of W⁶⁺ to W⁴⁵⁺ ions

Abstract

Tungsten ion densities are determined by measuring radial profiles of line emissions in LHD. Zn-(W44+) and Cu-like (W45+) ion densities are determined from line emission at 60.9 Å and 127.0 Å, respectively. Ion densities of W24+, W25+ and W26+ are also determined from tungsten pseudo-continuum (a so-called unresolved transition array (UTA)) at 29-33 Å. Observations of magnetic dipole (M1) forbidden lines at 3377Å enable evaluation of the ion density of W27+. In EAST tokamak the tungsten concentration is estimated by a combination of the UTA and total radiation loss. In HL-2A the tungsten influx is evaluated from line emission of W6+ ions at 216.2 Å and 261.4 Å, which are measured during the tungsten reappearance phase after tungsten laser blow-off. All these results demonstrate a good approach towards quantitative tungsten analysis.

Observation of line emissions from Ni-like W46 + ions in wavelength range of 7–8 Å in the Large Helical Device

“…After the tungsten pellet injection at 4.1 s, T e0 and W p quickly decreased, while n e increased. In our previous experiments, T e0 continued decreasing after the pellet injection and was sustained in a steady state with T e0 <1 keV [4][5][6][7][8][9][10][11][12]. On the other hand, ECH was resumed after the pellet injection in the present study to recover T e0 to observe the highly-ionized W ions.…”

“…In this wavelength range, the unresolved transition arrays (UTAs) consisting of the line emissions from W 23+ ~W33+ and W 24+ ~W29+ ions were observed at 19 ~ 33 Å and 47 ~ 54 Å, respectively. These UTA spectra are clear signals indicating that the W ions are successfully distributed in the plasmas by the pellet injection, which have been observed in many fusion plasma experiments related to W impurity studies [13,14]. The wavelength range of 6.5 ~ 10 Å of the spectra in Fig.…”

“…The coil system consists of a set of two continuous superconducting helical coils with poloidal pitch number of 2 and toroidal pitch number of 10, and also three pairs of superconducting poloidal coils. Spectroscopic studies for emissions released from W ions in a combination with a W pellet injection technique have been intensively conducted in LHD for contribution to the W transport study in W-divertor fusion devices represented by ITER and for the expansion of the experimental database of W line emissions [13][14][15][16]. As the results of the previous studies, the line emissions from W ions in low charge states, W 3+ ~W6+ , have been identified in the vacuum ultraviolet (VUV) range of 500 -1500Å [17].…”

“…Therefore, studies of W behaviors in high temperature plasmas are quite important for controlling W transport, which is necessary to establish a reliable operation scenario of fusion reactors. Spectroscopic studies for emissions released from W ions in a combination with a W pellet injection technique have been intensively conducted in the Large Helical Device (LHD), which is a heliotron type plasma confinement device, for contribution to the W transport study and for the expansion of the experimental database of W line emissions [4][5][6][7]. As the results of the previous studies, the line emissions from W ions in low charge states, W 3+ ∼W 6+ , have been identified in the vacuum ultraviolet (VUV) range of 500-1500 Å [8].…”

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

“…Spectroscopic studies for emission from W ions in combination with a tungsten pellet injection technique have been intensively conducted on the Large Helical Device (LHD) for contribution to tungsten transport studies in tungsten divertor fusion devices represented by ITER and for expansion of the experimental database of tungsten line emissions [11][12][13][14]. The electron temperature, T e , of the LHD core plasmas with a tungsten pellet injection ranges from 0.5 keV to 3.5 keV, which is close to that of the edge plasmas in ITER around the last closed flux surface, including the scrape-off layer.…”