Development of stress-free Laue diffraction crystal for X-ray beam splitting

In order to achieve the effective splitting of X-ray, the perfect crystal whose the space of lattice plane comparable to the X-ray wavelength can be used as beam splitter. This beam splitter utilizes the diffraction effect of Laue crystal to accurately manipulate X-ray beam. A stress-free crystal with thin thickness is crucial for high-quality X-ray splitting. The working area of crystal was thinned by acid etching. Additionally, the base of crystal was cut from a floating-zone silicon single-crystal ingot, which prevented the spread of stress to the working area of crystal in fabrication and experiment. The experiment of Laue diffraction was conducted at the synchrotron radiation facility. In order to obtain the inherent rocking curve and consistent imaging field of view, a non-dispersion configuration was employed to match the energy bandwidth of the incident beam with the Laue diffraction crystal. Then diffraction splitting within the energy bandwidth of the Laue crystal was achieved by utilizing a collimator to reduce the divergence of the incident beam. The fine structure of the diffraction curve was measured experimentally, and the slope error of linear fitting between the high-angle and low-angle positions of peaks is less than 0.4%, which satisfies the requirement of stress-free diffraction splitting. The design and characterization of this Laue diffraction crystal provide technical support for various applications, such as X-ray ghost imaging, X-ray multi-projection imaging, and beamline measurement at wavelength.