Studies in synchrotron x-ray microradiography: observation of biprism-typeinterference

Synchrotron x-ray microradiographic imaging is a routine and indeed essenti al prerequisite for the collection of diffraction data from a particular si ngle small crystallite embedded within a mat containing thousands of simila rly small-sized individuals when that particular small crystallite has been earmarked for a diffraction study, by reason of its special morphological features or optical properties, for example. The combination of optical mic roscopic, microradiographic and microdiffraction topographic techniques is proving fruitful in studies of CVD diamond crystallites. The simplest radio graphic contrast mechanism applying in the case of negligibly-absorbing obj ects is refractive deviation of the transmitted beams. However, the optimiz ation of experimental parameters for microradiography brings in factors suc h as Fresnel diffraction effects and incident-beam uniformity. When faceted objects are radiographed, re-entrants between facets produce the x-ray ana logue of the Fresnel biprism. Radiographic experiments are illustrated that plausibly demonstrate biprism interference, on the evidence of the fringe patterns observed.