On attaining eV energy resolution in an ionization energy shift at $\sim$ 60 keV

The K-line energy of high atomic number atoms depends to some degree on the atom's ionization stage, hence a high-resolution measurement of the K-line energy could, under the right circumstances, become a way to diagnose the plasma's ionization. Recently, we could measure a blue-shift close to $\sim$10 eV in the K$\alpha_2$ line of iridium ionized in the Plasma-Filled Rod Pinch. with a technique based on the line's transmission through a filter with a near-coincident K-edge. The presentation disxusses the measurements and analyses done to improve the systematic energy resolution to below 3 eV, with additional measurements and analysis of the K-ege filter with radiation from cold iridium excited with a PIXE source.