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

Abstract

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.