Comparison between two geometrical arrangements for diffraction enhanced imaging

Abstract

Diffraction enhanced imaging (DEI) with two crystals has been recently performed at the 4W1A beamline at the Beijing Synchrotron Radiation Facility (BSRF). In the first experiments, images collected with a set up where the rotation axis of the crystal was perpendieular to the orbit, show a higher quality with respect to those taken with a geometry with the rotation axis of the monochromatic crystal parallel to the orbit. When the rotation axis of the crystal is perpendicular to the orbit plane, e.g. to the polarization plane of the synchrotron radiation, the influence of both vibration and thermal expansion of the first crystal can be significantly reduced, allowing the collection of better images. In this work, a systematic comparison is male between two geometrical arrangements of crystals in DEI framework with respect to the reflectivity of crystals, spacial resolution, angular resolution and image contrast.