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Bragg Angles (bragg + angle)
Selected AbstractsThe fine structure of X-ray diffuse scattering in the vicinity of high-angle superlattice Bragg reflectionsACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2003Fine structure of X-ray diffuse scattering Triple-axis X-ray diffractometry was used to study diffuse scattering from an AlAs/GaAs superlattice grown on an [001]-oriented GaAs substrate by molecular beam epitaxy. Reciprocal-space maps were obtained around the 002 reflection from the superlattice and its low-angle first-order satellite. The data obtained reveal quasi-Bragg diffuse-scattering sheets caused by conformal behavior of interfacial roughness as well as amplification of diffuse scattering when the incoming or outgoing angle is nearly equal to the Bragg angle of the superlattice or substrate. The observed features of diffuse-scattering fine structure are explained within the framework of the distorted-wave Born approximation. Nevertheless, this approximation is shown to be incorrect for quantitative analysis of diffuse scattering. In particular, the observed domination in intensity of the incoming Bragg features over the outgoing ones is shown to reflect the decay rate of the coherent X-ray field through the diffuse-scattering channel, which is not negligible relative to the coherent diffraction. [source] X-ray diffraction topography using a diffractometer with a bendable monochromator at a synchrotron radiation sourceJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2002D. Altin The different properties of laboratory- and synchrotron-based double-crystal setups for X-ray topographic applications are discussed as a basis for the realization of a versatile instrument allowing the investigation of all kinds of crystals with high strain sensitivity and without any reduction in image size. It appears that the use of a bendable highly perfect monochromator (silicon) achieves this goal, through the local adaptation of Bragg angles, to compensate either dispersion or a bending of the sample. [source] A compact optical design for Bragg reflections near backscatteringJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2001Alfred Q. R. Baron A very compact in-line X-ray optical design is presented which is optimized for use with Bragg reflections close to backscattering (Bragg angles near 90°). The essential idea is to use a low-order Bragg reflection to couple the X-ray beam into a small channel-cut backscattering crystal. The design is demonstrated in an almost theoretically performing high-resolution monochromator providing 2 × 108 photons,s,1 in a 0.52,meV bandwidth at 25.65,keV. The monochromator is used to measure inelastic nuclear scattering from phonons in 161Dy-containing samples. [source] Synchrotron white-beam X-ray topography of ribonuclease S crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2002W. M. Vetter With careful experimental design, indexed synchrotron white-beam X-ray topographs of ribonuclease S crystals at ambient temperature could be recorded with a definition and contrast comparable to that of monochromatic beam topographs of other proteins reported in the literature. By excluding wavelengths longer than 1,Å from the white beam with a filter, a radiation dose equivalent to that required to record about 18 topographs could be tolerated without appreciable radiation damage to the samples. Bragg angles of 0.5° or less were required to select low-index harmonically pure reflections with high intensities and extinction lengths only several times the sample's thickness. The resulting X-ray topographs in some cases showed topographic detail and in others showed the even featureless background that has been considered characteristic of a protein crystal of low mosaicity. The ribonuclease S crystals were well ordered single crystals of a quality comparable to other protein crystals that have been studied by X-ray topography. [source] | ||||||||||