Influence of the vertical divergence of beams in the X-ray double-crystal arrangement

A theoretical investigation is made into the vertical divergence effect of incident beams in the X-ray double-crystal arrangement, with dynamical diffraction effects taken into consideration. Equations describing the relation between the vertical divergence and the angular position of the second crystal under a condition of constant diffraction intensity are derived for the cases of parallel and non-parallel settings. These equations serve as a sufficient basis for explaining and analyzing problems relating to the vertical divergence effect.