Effect of diffractive channeling on coherent-bremsstrahlung spectra

An experiment to detect the dependence coherent-bremsstrahlung spectra on the diffractive channeling of electrons and positrons in a single-crystal is described. The electron beam with an energy of 100 keV was used to initiate the bremsstrahlung radiation in a single-crystal copper target 400 A thick. Bremsstrahlung photons were detected by a semiconductor silicon detector with an energy resolution of about 300 eV. It is found that the bremsstrahlung spectra exhibited the expected peaks at the high-energy edges. The intensity of the overall spectrum exhibited a clear dependence on the orientation of the beam: intensity was at maximum when the electrons were incident along the 100 direction of the crystal, and at minimum (22 percent lower) when the crystal was rotated through an angle of 2.5 deg. It is pointed out that the orientation dependence should be more pronounced in the case of a chain of lattice sites.