On the theory of an X-ray Fabry-Perot interferometer

The theory of an X-ray Fabry-Perot interferometer (FPI) is developed as a p articular case of the dynamical theory of X-ray Bragg diffraction in layere d crystalline systems. Mathematical expressions ale derived fur the transmi ssivity and reflectivity of the X-ray FPI built as a system of two perfect crystal plates parallel to each other. The performance of the X-ray PPI is similar to that of the optical FPI. Both show fine interference structure i n the transmission and reflection dependences. However, for the X-ray FPI t his occurs only inside the region of the Bragg back diffraction peak. The i nfluence of possible imperfections, such as the roughness of the crystal pl att surfaces and the error in the parallelism of the atomic planes are disc ussed. It is shown that both factors map significantly deteriorate the perf ormance of the X-ray FPI. Numerical estimations are given.