Spectra of W$^{39+}$-W$^{47+}$ in the 12 nm to 20 nm region observed with an EBIT light source

TL;DR

This study used an EBIT light source to observe and identify spectral lines of highly ionized tungsten in the extreme ultraviolet, providing new line identifications and confirming previous results with high precision.

Contribution

The paper presents new spectral line identifications for tungsten ions W$^{39+}$ to W$^{47+}$ in the 12-20 nm range, with improved wavelength accuracy and validation through collisional-radiative modeling.

Findings

Good agreement between observed spectra and modeling results.

New line identifications for several tungsten ionization stages.

Wavelength uncertainties range from 0.002 to 0.010 nm.

Abstract

We observed spectra of highly ionized tungsten in the extreme ultraviolet with an electron beam ion trap (EBIT) and a grazing incidence spectrometer at the National Institute of Standards and Technology. Stages of ionization were distinguished by varying the energy of the electron beam between 2.1 keV and 4.3 keV and correlating the energies with spectral line emergence. The spectra were calibrated by reference lines of highly ionized iron produced in the EBIT. Identification of the observed lines was aided by collisional-radiative modeling of the EBIT plasma. Good quantitative agreement was obtained between the modeling results and the experimental observations. Our line identifications complement recent results for W$^{40+}$-W$^{45+}$ observed in a tokamak plasma by P\"{u}tterich {\it et al} (\jpb {\bf 38}, 3071, 2005). For most lines we agree with their assignment of ionization stage. Additionally, we present new identifications for some allowed and forbidden lines of W$^{39+}$, W$^{44+}$, W$^{46+}$, and W$^{47+}$. The uncertainties of our wavelengths range from 0.002 nm to 0.010 nm.