Diffraction capability with different kind of crystals disposed in geometry 2, considering a white X-ray beam impinging on the plate. a) Perfect crystal. If the Bragg condition is satisfied, a precise wave length is diffracted and the efficiency is dependent on the thickness traversed. The integrated reflectivity is very low. b) Mosaic crystal. The integrated diffraction efficiency is higher with respect to case a), though the diffraction efficiency is limited at 50% and the spatial resolution of the diffracted photons is limited by the mosaic defocusing effect. c) Bent crystal but without QM curvature. The primary curvature allows the focalization of the diffracted photons, however, the flat diffracting planes reduce the integrated intensity. d) Bent crystal with QM curvature. QM sample combines the focusing action due to the primary curvature with the high reflectivity of CDP built up by quasi-mosaicity.