X-ray Bragg diffraction in asymmetric backscattering geometry |
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Authors: | Shvyd'ko Yu V Lerche M Kuetgens U Rüter H D Alatas A Zhao J |
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Institution: | Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA. shvydko@aps.anl.gov |
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Abstract: | We observe three effects in the Bragg diffraction of x rays in backscattering geometry from asymmetrically cut crystals. First, exact Bragg backscattering takes place not at normal incidence to the reflecting atomic planes. Second, a well-collimated (approximately 1 microrad) beam is transformed after the Bragg reflection into a strongly divergent beam (230 microrad) with reflection angle dependent on x-ray wavelength--an effect of angular dispersion. The asymmetrically cut crystal thus behaves like an optical prism, dispersing an incident collimated polychromatic beam. The dispersion rate is approximately 8.5 mrad/eV. Third, parasitic Bragg reflections accompanying Bragg backreflection are suppressed. These effects offer a radically new means for monochromatization of x rays not limited by the intrinsic width of the Bragg reflection. |
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