Studies in synchrotron x-ray microradiography: observation ofbiprism-type interference

Abstract

Synchrotron x-ray microradiographic imaging is a routine and indeed essential prerequisite for the collection of diffraction data from a particular single small crystallite embedded within a mat containing thousands of similarly 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 microscopic, microradiographic and microdiffraction topographic techniques is proving fruitful in studies of CVD diamond crystallites. The simplest radiographic contrast mechanism applying in the case of negligibly-absorbing objects is refractive deviation of the transmitted beams. However, the optimization of experimental parameters for microradiography brings in factors such as Fresnel diffraction effects and incident-beam uniformity. When faceted objects are radiographed, re-entrants between facets produce the x-ray analogue of the Fresnel biprism. Radiographic experiments are illustrated that plausibly demonstrate biprism interference, on the evidence of the fringe patterns observed.