Formation of interference fringes in the Bragg-(Bragg)m-Laue mode.

X-ray interference fringes in the beams diffracted from a lateral surface of a thin plane-parallel crystal are measured and analyzed using Wagner's approach [Wagner (1956), Z. Phys. 146, 127-168]. It is found that the fringes are caused by the interference between the internal waves excited by the incident beam in both the Bragg-Laue case and the Bragg-Bragg-Laue case. The period of the interference fringes is shown to be proportional to the distance between the incident point of the X-ray and the crystal edge, and to be inversely proportional to the crystal thickness.