X-ray diffraction with a Bragg angle near pi/2 and its applications.

X-ray dynamical diffraction phenomena at a Bragg angle near pi/2 are studied. The X-ray transmissivity as well as the reflectivity from the (991) lattice plane of a silicon thin plate is observed. It agrees fairly well with the diffraction pattern calculated on the basis of the Darwin approach. The possibility is discussed whether a set of two crystal plates arranged face to face, in which the diffraction condition with a Bragg angle near pi/2 is satisfied, may be used as a very high resolution monochromator.