Experimental x-ray spectrum (black line) measured by the FSSR spectrometer as emitted from a C₂F₄ target. What is recorded is the spectrum of sulfur impurities in the third order of reflection. Overlaid are simulations performed using the PrismSPECT code (red, olive, and blue curves) for the target surface region, using the group of satellites sensitive to the plasma parameters. For all temperatures shown in the figure, the electron density was N_e = 7 × 10²⁰ cm⁻³. All curves are normalized to the S He_α line. The best fitting corresponds to the red curve. The inset shown in the top left corner demonstrates the detailed fitting of the satellites of the experimental spectrum. The arrows point to the lines with the best fit.