Study on the methods for diffraction-enhanced imaging with two crystals

Diffraction-enhanced imaging by using two crystals has been recently developed in x-ray topography station in Beijing Synchrotron Radiation Facility. In this article the analysis for the influence of the thermal expansion of the first crystal on the diffraction enhanced imaging is presented. The conclusion is that the influence of the thermal expansion of the first crystal can be avoided and much better images can be obtained when the axes of crystals are placed vertically to the polarization plane of the synchrotron radiation. The experimental results confirmed this analysis. (authors)