X-Ray and EUV Spectroscopy of Highly-Charged Ions of Tungsten

We report on recent measurements and collisional-radiative simulations of x-ray and EUV spectra from multiply-charged ions of tungsten produced with the Electron Beam Ion Trap (EBIT) at the National Institute of Standards and Technology (NIST). The spectra were recorded in the ranges of 0.3 nm to 1 nm and 4 nm to 20 nm for beam energies varied between 2 and 4.3 keV. A quantum microcalorimeter was used for x-ray measurements while the EUV spectra were recorded with a grazing incidence spectrometer. of 4.08 keV. The uncertainties of our measured wavelengths range from 0.002 to 0.010 nm. 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 new spectral lines from W39+, W44+, W45+, W46+, and W47+ ions, led to the reinterpretation of a previously known line in the Ni-like ion as an overlap of electric-quadrupole and magnetic-octupole lines, and revealed subtle features in the spectra arising from the dominance of forbidden transitions between excited states. The importance of level population mechanisms specific to the EBIT plasmas is discussed as well