Study on the X-ray mirror quality specification in advanced light source

The influence of the X-ray mirror errors on the performance of the beamline increases as the X-ray beam's coherence improves in advanced light sources. The spatial dispersion of the X-ray beam is crucial for spatial resolution and field of view. However, selecting the appropriate merit function for expressing light distribution and identifying its relationship to optical error is very important in beamline design. We develop a high-efficiency wave-optics simulation platform and a deterministic analysis model to address this issue. The simulation experiments evaluated merit functions, including Strehl ratio, root-mean-square spot size, and encircled energy radius. We proved that the encircled energy radius is a good metric of the x-ray beam spatial dispersion, which matches the results of the Church-Takacs theory. In addition, it is found that limiting the contribution of the low frequency ( wavelength > 1/10 L ) error is effective for specifying the requirements of X-ray mirrors.

Automated summary

The influence of X-ray mirror errors on beamline performance increases with the improvement of X-ray beam coherence in advanced light sources. Selecting appropriate merit functions to express light distribution and understanding their relationship to optical error is crucial in beamline design. A high-efficiency wave-optics simulation platform and deterministic analysis model were developed to address this issue. The encircled energy radius was proven to be a good metric for the spatial dispersion of the X-ray beam, matching the Church-Takacs theory. It was also found that limiting the contribution of low-frequency errors is effective for specifying the requirements of X-ray mirrors.