Sensitivity and S/N-ratio of superconducting high-resolution X-ray spectrometers

Superconducting tunnel junction (STJ) X-ray spectrometers have been developed for synchrotron-based high-resolution soft X-ray spectroscopy. We are quantifying the improvements in sensitivity and signal-to-noise ratio that STJ spectrometers can offer for the analysis of dilute specimens over conventional semiconductor and grating spectrometers. We present analytical equations to quantify the improvements in terms of spectrometer resolution, detection efficiency and count rate capabilities as a function of line separation and spectral background. We discuss the implications of this analysis for L-edge spectroscopy of first-row transition metals.