REFLECTIVITY CURVES OF BRAGG-REFLECTIONS FROM SMALL IMPERFECT SINGLE-CRYSTALS

A slice-scan procedure involving a narrow aperture in front of the detector can allow determination of the extinction-affected reflectivity curve, r*(Delta omega), of Bragg reflections from a small imperfect single crystal. The measured curve can be corrected for the effect of the remaining truncated components, associated with the source emissivity and wavelength distributions which are passed by the narrow aperture. Because of the small area of diffraction space associated with this procedure compared with that for the conventional wide-aperture reflection profile, contributions from TDS, air scatter and incoherent radiation are greatly reduced. By the very nature of reflectivity curves, their determination does not involve a systematically increasing Delta omega angular range dependent on tan theta.