Tungsten spectroscopy in the EUV range observed at a high-temperature superconducting electron-beam ion trap

We have recorded extreme ultraviolet spectra from W11+ to W15+ ions using a flat-field spectrometer installed at the Shanghai high-temperature superconducting electron-beam ion trap. The spectra were recorded at beam energies ranging between 200 and 400 eV and showed spectral lines and transition arrays in the 170-260 angstrom region. The charge states and spectra transitions were identified by comparison with calculations using a detailed relativistic configuration interaction method and collisional-radiative model, both incorporated in the flexible atomic code. Atomic structure calculations showed that the dominant emission arises from 5d --> 5p and 5p --> 5s transitions. The work also identified the ground-state configuration of W13+ as 4f(13)5s(2) both theoretically and experimentally.