The polarization of radiation emitted by planar channeling relativistic electrons with an energy on the order of 1 GeV in a thick diamond crystal has been studied theoretically and experimentally. A ''thermal-layer'' model has been used to calculate radiation in a thick crystal.

The experimental setup is described, and the angular dependence of the asymmetry Sigma(p,n)(theta) of the cross section for the reactions He-4(gamma, p)T and He-4(gamma, n)He-3 induced by 40-, 60-, and 80-MeV linearly polarized photons is measured. The asymmetry Sigma(p,n)(theta) calculated in the relativistic gauge-invariant approach is in satisfactory agreement with experimental data on this asymmetry, with the exception of the asymmetry of the cross section for the reaction (gamma, n) at E(gamma) = 60 MeV and theta = 90 degrees - 120 degrees. In the last case, the theoretical value is close to unity, while the experiment yields Sigma(n)(theta) = 0.47 +/- 0.18.

The experimental results of the development of electromagnetic showers induced by 28 GeV electrons in aligned tungsten crystals with thicknesses 0.07,0.3,1.0mm are presented. At this energy of electrons the “constant strong field” effect starts to show and the development of showers in aligned crystals is distinguished from the one in an amorphous substance.

The differential cross sections dsigma(parallel-to)/dOMEGA and dsigma(perpendicular-to)/dOMEGA for photodisintegration of the deuteron by linearly polarized photons have been measured over the photon energy range 250-500 MeV for proton emission angles of 90-degrees, 105-degrees, 120-degrees, and 135-degrees in the c.m. frame. The experimental results are compared with predictions of a theory which incorporates possible excitation of dibaryon resonances.

An experimental study has been made of the development of electromagnetic showers generated along the [111] axis of a tungsten crystal 1.0 mm thick by gamma rays with energies of 8-27 GeV.

The orientation dependence of the high-energy component of the secondary-emission current has been studied on a diamond single crystal. This is the first such study. This effect could in principle be utilized to orient a diamond platelet with respect to an electron beam.

The radiation losses for 28 GeV electrons in the [111] axis-oriented tungsten crystals of the 1 and 0,3 mm thickness are measured. The radiation loss calculations performed in the framework of the coherent theory and constant field approximation agree with the experimental data within the 10% accuracy. The relative radiation losses of electrons with the energy below 1 GeV in the same crystals are given.

The differential cross sections of the deuteron-photodisintegration reaction have been measured for outgoing proton angles 90-degrees, 105-degrees, 120-degrees, and 135-degrees in the c.m.s. in the photon energy range 250-500 MeV. The results of the measurements are compared with calculations including possible excitation of dibaryon resonances.

The position of a source of gamma-quanta with energies greater than or similar to 1 Ge V can be determined using a crystal converter by recording the charged component of the shower that develops in a crystal. The method can be applied in gamma astronomy to produce crystal gamma telescopes.

An automated goniometer is described for the production of quasimonochromatic linearly polarized photons by a coherent-bremsstrahlung method in single crystals in the beam of the Khar'kov 2-GeV linear electron accelerator. The single-crystal target is oriented in the goniometer by rotation about two mutually perpendicular axes with an angle-reading accuracy of 5.10(-5) rad. Rotation about the azimuthal axis of revolution within 0-22-degrees is used to adjust the single crystal in the beam. The direction of the photon-polarization vector is changed by rotation of the target about the axis of the electron beam with 0.1-degrees accuracy. The Kristall-2 goniometer is controlled by an Elektronika-60 microcomputer and an SM-4 higher-level computer.

The asymmetry of the cross sections for inclusive photoproduction of charged pions has been studied as a function of the atomic number of the target for the nuclei Li-6, Li-7, Be-9, C-12, Al-27, and W-184. The pion emission angle was 90-degrees in the laboratory frame. The peak in the coherent bremsstrahlung was at an energy of 350 MeV. The asymmetry decreases from 0.57 at A = 1 to 0.26 at A congruent-to 20 and then remains essentially constant at higher values of A.

Calculations, according to the theory of coherent bremsstrahlung, of the polarization of {gamma} radiation arising in motion of relativistic electrons near the {l angle}110{r angle} axis and the (001) plane of diamond single crystals of thicknesses 0.3 and 2 mm are compared with the results of experimental investigations at electron initial energies 1200 and 794 MeV.