Optimisation of coherent X-ray diffraction imaging at ultrabright synchrotron sources

摘要

Coherent X-ray Diffraction Imaging (CXDI) is a powerful method of imaging single crystalline grains within a powder. Direct Fourier transformation of the oversampled diffraction pattern surrounding a Bragg peak is possible once the phases have been obtained using ai 'support' constraint. The image is in general complex with the phase representing a jproecton of the atomic displacements allowing access to the internal strains inside the crys- tal. CXDI relies crucially on the production of a coherent beam of X-rays, which is one of the technical advances of the latest 3rd generation Synchroton Radiation (SR) sources. It is shown here how the use of a secondary source in the design of the X-ray beamline allows the coherence to be controlled continuously over a finite range without any loss of flux. The conclusions will have significant impact on instruments currently being designed at the Dia-mond Light Source and the new National Synchrotron Light Source (NSLS-2).