Two diffraction schemes for widely divergent beam of X-ray radiation

Peculiarities of two diffraction schemes: d-c (diaphragm-crystal) and c-d (crystaldiaphragm) for widely divergent beam of X-ray radiation are considered. It is determined and experimentally confirmed that in c-d scheme the diffraction image is a topographic map of the studied area of the crystal. It is also determined that in the d-c scheme, when L = 2l (l and L are, respectively, the crystal and the photographic plate distances from the diaphragm) the branches of the hyperbolas, formed by the characteristic radiations Kα and Kβ (including reflections of the second and the third orders) merge into one straight line in the given family of the planes (hkl). It is experimentally determined that the character of confluence is very sensitive to the structural imperfections of the crystal under study.