The analytical performance of Micro-XRF instruments depends on the measurement conditions. Parameters have to be selected carefully according to the required task:
The spatial resolution of a position-sensitive measurement is influenced by different factors like spot size, step size, and measured intensity.
The spot size is one of the main factors that influence the spatial resolution of images. It is usually measured with the knife edge method. This technique measures the beam intensity as a function of the position will performing a line scan across the shap edge of a material.
Other factors influencing the spatial resolution of elemental distribution images are the pixel size and the contrast between pixels. In Micro-XRF the pixel size is determined not only by the spot size but also by the step size. The spatial resolution can be improved if the step size is smaller than the spot size. On the other hand, a minimum level of intensity is required for good contrast between neighboring pixels. The pixel intensity can be changed by varying the acquisition time per pixel. According to these facts, the step size and the pixel intensity have to be optimized for a given spot size.