The extreme ultraviolet emissions of W²³⁺(4f⁵)

In order to comply with the special challenges (open 4f-shell, configuration mixing) of simulating the spectrum of W²³⁺ an extensive atomic model was implemented using the flexible atomic code (FAC). In detail, the basis functions from 11 configurations were used to model about 12000 levels, which give rise to roughly 60 million transitions including nearly 6 million electric and magnetic dipole transitions. A collisional radiative model has been put together which could handle the size of the input data. The modelled spectra (4-40 nm) show low sensitivity on the electron density, which validates the comparison of EBIT and tokamak spectra. The emissions between 4 and 7 nm are discussed in the context of the observations at fusion plasmas. In this range, the influence of W²³⁺ is limited due to the small contribution to the measurement - however, elements of the presented modelling might explain the second, not understood spectral feature at 6 nm. Further details of the spectra are only briefly discussed as a close comparison to experimental data requires also models for the neighbouring ionisation stages. Additionally, the importance of configuration mixing becomes apparent motivating further investigations on neighbouring ionisation stages with similarly complex models.