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

Abstract

We present detailed collisional-radiative modeling for a benchmark x-ray spectrum of highly charged tungsten ions in the range between 3 and $10\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ produced in an electron beam ion trap (EBIT) with a beam energy of $4.08\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. 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 ${\mathrm{W}}^{45+}$ and Ni-like ${\mathrm{W}}^{46+}$ 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.