Measurement of nano-positioning cross-chamber for Kirkpatrick-Baez mirror and sample stage of synchrotron light source

Nano-positioning is always a critical issue for nano-experiments of ptychography, Bragg Coherent Diffractive Imaging (Bragg-CDI), and Wide-Angle X-ray Scattering X-ray Photon Correlation Spectroscopy (WAXS-XPCS) in the field of synchrotron light sources. Owing to the limited working distance of Kirkpatrick-Baez mirrors (KB-mirror) and the crowded and complicated layout of the experimental apparatus, it is difficult to accurately measure the relative positioning of a KB-mirror and a sample stage located in separate chambers. To address this challenge, a direct measurement method based on gratings and a heterodyne interferometer is proposed. The principle and system configuration are presented through theoretical derivation and experimental validation with building prototype. Furthermore, the test result of 4 nm resolution was achieved by a step motion experiment. The proposed method not only inherits the advantages of high-accuracy and non-contact measurement of a typical laser heterodyne interferometer but also overcomes its inherent insensitivity to lateral displacement. As such, it provides a compact and effective solution for cross-chamber nano-positioning.