“…When a relativistic electron transverses the single crystal layer of the target, its Coulomb field is scattered on a system of parallel atomic planes of the crystal, producing parametric X-ray radiation (PXR) [7][8][9], with the PXR photons moving together with the DTR photons along the Bragg scattering direction. The process of coherent X-ray scattering of relativistic electrons in a crystal, including PXR and DTR, was developed in [10][11][12][13][14] within the framework of a two-wave approximation of the dynamic theory of X-ray diffraction. It is noteworthy that in [10,11] coherent X-ray radiation is treated in a particular case of symmetrical reflection, where the reflecting system of atomic planes of a crystal is parallel with respect to the surface of the target in the case of the Bragg scattering geometry and normal to it in the case of the Laue scattering geometry.…”