EUV spectra of highly-charged ions W$^{54+}$-W$^{63+}$ relevant to ITER diagnostics

TL;DR

This paper presents the first EUV spectral measurements of highly-charged tungsten ions W$^{54+}$ to W$^{63+}$ using EBIT, identifying key spectral lines for fusion diagnostics and analyzing their implications for impurity transport and plasma modeling.

Contribution

It provides the first detailed EUV spectra of W$^{54+}$ to W$^{63+}$ ions and confirms line identifications through isoelectronic comparisons, enhancing fusion plasma diagnostics.

Findings

Identified strong electric- and magnetic-dipole transitions in W ions.

Confirmed spectral line identifications with isoelectronic spectra.

Highlighted the role of charge exchange in plasma modeling.

Abstract

We report the first measurements and detailed analysis of extreme ultraviolet (EUV) spectra (4 nm to 20 nm) of highly-charged tungsten ions W$^{54+}$ to W$^{63+}$ obtained with an electron beam ion trap (EBIT). Collisional-radiative modelling is used to identify strong electric-dipole and magnetic-dipole transitions in all ionization stages. These lines can be used for impurity transport studies and temperature diagnostics in fusion reactors, such as ITER. Identifications of prominent lines from several W ions were confirmed by measurement of isoelectronic EUV spectra of Hf, Ta, and Au. We also discuss the importance of charge exchange recombination for correct description of ionization balance in the EBIT plasma.