Hard X-ray shearing interferometry

Abstract
We have developed a hard x-ray interferometer known in visible and EUV optics as shearing interferometer. In contrast to the well known Bonse-Hart interferometer, the interfering beams are not completely separated into object and reference beams, but they are merely sheared by a small angle, so that both beams pass through the sample. We used silicon phase gratings generated by electron beam lithography and wet chemical etching as beam splitter and analyzer elements. The technique was tested successfully at 2.4 keV and 24.8 keV photon energies by using polystyrene spheres as low absorbing test objects. The interferometer proved to be insensitive to mechanical vibrations and drift. We obtained micrographs with Moire patterns of good visibility. The local distortions of the interference pattems result from the local gradient in phase shift caused by the test objects. For a pcrfoetly aligned and divergence compensated setup, the phase map of low absorbing objects can bc rctrieved by using a simple numerical integration.