Direct Observation of the M1 Transition between the Ground Term Fine Structure Levels of W VIII

Abstract

Abstract:We present a direct observation of the M1 transition between the fine structure splitting in the 4 f 13 5s 2 5p 6 2 F ground term of W VIII. The spectroscopic data of few-times ionized tungsten ions are important for the future ITER diagnostics, but there is a serious lack of data. The present study is part of an ongoing effort to solve this problem. Emission from the tungsten ions produced and trapped in a compact electron beam ion trap is observed with a Czerny-Turner visible spectrometer. Spectra in the EUV range are also observed at the same time to help identify the previously-unreported visible lines. The observed wavelength 574.47 ± 0.03 nm (air), which corresponds to the fine structure splitting of 17,402.5 ± 0.9 cm −1 , shows reasonable agreement with the previously reported value 17,410 ± 5 cm −1 obtained indirectly through the analysis of EUV spectra [Ryabtsev et al., Atoms 3 (2015) 273].

Emission Lines in 290–360 nm of Highly Charged Tungsten Ions W20+–W29+

“…Recently, a local tungsten density in core plasmas of the LHD was successfully assessed with near-UV magnetic-dipole (M1) lines emitted by W 26+ and W 27+ ions [13]. Such visible and near-UV emission lines of highly charged W ions were intensively measured by different research groups, using electron-beam-ion-traps (EBITs): W 7+ -W 9+ [14,15], W 8+ -W 28+ [16], W 11+ [17], W 12+ -W 14+ [18], W 13+ [19], W 24+ -W 25+ [20], W 25+ [21], W 26+ [22,23], W 26+ -W 33+ [24], W 27+ [25], W 28+ [26,27], and W 52+ [28][29][30]. However, charge state identification still remain uncertain for many lines observed at LHD.…”

Extreme ultraviolet spectra of multiply charged tungsten ions

“…W 6+ and W 7+ , experimental data obtained with spark plasma are available for the vacuum ultraviolet to extreme ultraviolet (EUV) region [6,7,8]. Recently, observation with an electron beam ion trap (EBIT) has also been done [4,9]. For higher charge states, e.g.…”

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

“…Moreover, several small peaks were found at around 198-202 Å in Figure 6d. They are probably W 7+ lines because the spectral shape is similar to that of the W 7+ spectrum identified in EBIT experiments [33,34]. The emission of W 7+ ions in this wavelength region has been identified in detail through vacuum spark experiments with high-resolution spectroscopic diagnostics [35,36].…”