Accurate modeling of benchmark x-ray spectra from highly charged ions of tungsten

We present detailed collisional-radiative modeling for a benchmark x-ray spectrum of highly charged tungsten ions in the range between 3 and 10 Å produced in an electron beam ion trap (EBIT) with a beam energy of 4.08 keV. Remarkably good agreement between calculated and measured spectra was obtained without adjustable parameters, highlighting the well-controlled experimental conditions and the sophistication of the kinetic simulation of the non-Maxwellian tungsten plasma. This agreement permitted the identification of spectral lines from Cu-like W⁴⁵⁺ and Ni-like W⁴⁶⁺ ions, led to the reinterpretation of a previously known line in Ni-like ion as an overlap of electric-quadrupole and magnetic-octupole lines, and revealed subtle features in the x-ray spectrum arising from the dominance of forbidden transitions between excited states. The importance of level population mechanisms specific to the EBIT plasma is discussed as well.