Specimen homogeneity requirements for EDS in high count rate mode
This work describes limits with pile-up correction considering EDS spectra evaluation in the case of processing high count rate spectra from inhomogeneous specimen areas. The pulse processor pile-up rejection has some limitations with detection of X-ray event coincidences. Therefore, remaining pile-up artefacts are always present in measured spectra and it is necessary to consider these artefacts to avoid mistakes in qualitative and quantitative results. Any pile-up calculation is based on probabilities for coincidences of X-rays, some of which cannot be resolved by pile-up rejection due to the constantly limited time resolution. A fundamental assumption with all calculation approaches is the time-related random distribution of emitted X-rays. This rule is violated with spectra from inhomogeneous specimen areas. Examples are shown and opportunities to avoid the fundamental shortcoming are discussed.