Towards high‐flux X‐ray beam compressing channel‐cut monochromators

The issue of a high‐flux X‐ray beam compressing channel‐cut monochromator for applications in X‐ray metrology is addressed. A Ge(111) compressor with compression ratio 20.3 was designed on the principle of a combination of symmetric and highly asymmetric diffractions. A pilot application of the single‐point diamond technology (SPDT) to finish active surfaces of X‐ray optics was tested, providing 50% flux enhancement as compared to a Ge(220) counterpart prepared by traditional surface treatment. This is much more than the theoretical 22% forecast and shows the potential of SPDT for preparation of high‐flux X‐ray compressors with a high compression ratio, where highly asymmetric diffraction with a very low exit angle is inevitable. The implications for efficient collection of X‐rays from microfocus X‐ray sources are discussed. A comparison of Ge compressors with Ge parallel channel‐cut monochromators combined with a 50 µm slit shows the several times higher flux of the former, making them applicable in X‐ray diffraction experiments at medium resolution. Furthermore, the Ge(111) compressor was tested as a collimator in high‐resolution grazing‐incidence small‐angle X‐ray scattering (GISAXS) measurements of surface gratings, providing experimental resolution close to 400 nm. This is ∼100 nm smaller than that achieved with the Ge(220) compressor but still approximately twice that of commercial SAXS/GISAXS laboratory setups.