8 September 2009 Analysis of a spatial structure of a focused x-ray beam diffracted from crystals
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Spatial structure of a focused beam diffracted from crystals of different thickness was studied experimentally at the ESRF optical beamline BM5. The beam was focused by a planar parabolic refractive lens. Si (111) thick crystal and 8 μm and 50 μm thick perfect Si(111) crystals positioned between the lens and the focus were used as model samples. The structure of the beam was analyzed at the focus of the lens by using a knife edge scan and a high-resolution CCD camera. The broadening of the focused beam due to the extinction effect was experimentally measured and compared with theoretical predictions. For a sufficiently thin crystal a second peak was experimentally observed which is due to the reflection from the back surface. We found also that the spatial structure depends on whether the crystal diffracts strongly (dynamically) or weakly (kinematically). In the later case, both surfaces of the crystal effectively reflect as mirrors with the reduced reflectivity and the relative intensity of the two peaks is determined by absorption. Theoretical simulations show excellent agreement with experiment.
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A. Kazimirov, A. Kazimirov, V. Kohn, V. Kohn, A. Snigirev, A. Snigirev, I. Snigireva, I. Snigireva, "Analysis of a spatial structure of a focused x-ray beam diffracted from crystals", Proc. SPIE 7448, Advances in X-Ray/EUV Optics and Components IV, 74480P (8 September 2009); doi: 10.1117/12.826082; https://doi.org/10.1117/12.826082

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