SPECTRAL-ANGULAR DISTRIBUTION AND POLARIZATION OF SURFACE PARAMETRIC X-RAY-RADIATION OF A RELATIVISTIC CHARGED-PARTICLE

Surface parametric (quasi-Cherenkov) X-ray radiation (SPXR) of a relativistic charged particle, moving at a small angle with the crystal surface, is considered. The spectral-angular distribution and polarization characteristics of the radiation are found. It is shown that at sufficiently small angles of electron incidence on the crystal surface the main contribution to the surface radiation intensity is made by the vacuum part of the trajectory. In this case multiple scattering does not essentially affect the radiation process. It is shown that X-ray quanta with different degree of circular polarization can be obtained by rotation of the crystal with respect to the particle trajectory. At energies above 100 MeV the fine structure in the SPXR angular distribution consists of two peaks spatially separated by the angle of emission and polarized elliptically with a sense of rotation opposite to that of the electric field vector. The possibility of experimental observation of the radiation described is discussed.