Systematic-error-free wavefront measurement using an X-ray single-grating interferometer

In this study, the systematic errors of an X-ray single-grating interferometer based on the Talbot effect were investigated in detail. Non-negligible systematic errors induced by an X-ray camera were identified and a method to eliminate the systematic error was proposed. Systematic-error-free measurements of the wavefront error produced by multilayer focusing mirrors with large numerical apertures were demonstrated at the SPring-8 Angstrom Compact free electron LAser. Consequently, wavefront aberration obtained with two different cameras was found to be consistent with an accuracy better than λ/12.