The formation of the X-ray phase contrast under the diffraction focusing of the spherical wave

Abstract

The study of the inner structure of the weak-absorbing noncrystalline materials as well as the biological objects is carried out by the method of the X-ray phase contrast which at present is substantially in progress. In the present work the possibility of reconstructing the inner structure of the one-dimensional phase objects under the diffraction focusing of the X-ray spherical wave is reported.The fact that with the incidence of the monochromatic X-ray spherical wave on the crystal in Laue geometry the diffracted radiation is focused inside the crystal is used. The focal line is perpendicular to the diffraction plane. Before entering the crystal the radiation is supposed to pass through the phase object where the inhomogeneities have one-dimensional distribution along the perpendicular diffraction plane. With the wave transmission trough the phase object the conditions of the focusing are broken: because of the refraction on the inhomogeneities the X-rays change their directions and the wave front is deformed. The intensity distribution analysis in the image diffracted from a strong-absorbing wedge-like crystal with rib parallel to the diffraction vector shows that the focusing is possible for every point of the phase object if one compensates the deviation from Bragg condition along the diffraction vector and the wave front deformation along the perpendicular diffraction plane. The focusing is possible if the source-crystal distance is smaller than the ratio of the inhomogeneity size and the difference of the index of refraction from the unit.