Investigation of Tungsten Unresolved Transition Array Spectrum around 300 Å for Fusion Plasma Diagnostics

Tungsten spectroscopic studies have attracted much attention, because tungsten will be used as a plasma- facing component in ITER and future DEMO reactors. However, spectral line data of tungsten ions in low to intermediate charge states, such as W⁸⁺-W²⁶⁺, is still lacking. To accumulate spectral line data of W⁸⁺-W²⁶⁺, it is very important to identify the charge state and transition of Unresolved Transition Array (UTA) spectrum, as well as discrete line spectrum. In this study, we investigated electron temperature dependence of a UTA spectrum around 300 Å for an advanced understanding of spectral line shape. As a result, the UTA spectrum contains W¹⁷⁺- W²⁷⁺ and emission line from 5s-5p transition and its satellite line from 5s²-5s5p transition are strongly emitted. It was suggested that the UTA spectrum around 300 Å will be useful for diagnostics of ITER edge plasma.