Dynamical diffraction effect in a curved multi-plate crystal cavity.

A modified algorithm for X-ray dynamical diffraction theory is presented for curved boundary crystals and a detailed description of the numerical procedure is given. The simulated and experimental results both show an anomalous focusing behavior in a curved multi-plate crystal cavity of silicon under the (12,4,0) back-diffraction condition at a photon energy of 14.4388 keV. The focusing effects are analyzed, within the framework of the dynamical theory of X-ray diffraction, from the excitation of the dispersion surface and modification of the index of refraction with respect to the non-plane-parallel boundaries of a curved crystal cavity.