Generation of X rays at the grazing incidence of 18-MeV electrons on a thin Si crystal in a betatron chamber

The generation of X rays at the grazing incidence of 18-MeV electrons with a 50-$\mu$m-thick Si crystal 4 mm in length along the electron beam has been studied. The crystal has been placed in a goniometer inside the chamber of a B-18 betatron. The results exhibit strong changes in the angular distribution of bremsstrahlung at the variation of the orientation of the crystal. This effect is not observed in the case of the normal incidence of electrons on the surface of a thin crystal where the channeling of electrons, which occurs at certain orientation of the crystal, is absent. Images of a reference microstructure have been obtained with a high resolution of details of the microstructure owing to the smallness of the source of radiation. The dependence of the contrast of an image on the position of the microstructure in the radiation cone has been demonstrated.