Radiation from relativistic electrons in homogeneous condensed matter at large angles (≫γ−1)

The radiation spectra from 900 and 400 MeV electrons in thin Ta, Cu, and Sn foils are measured at an angle of 19° with respect to the direction of motion of the beam. The radiation yield and its dependence on the electron energy agree satisfactorily with the theory of polarization bremsstrahlung. This result represents the first direct observation of polarization bremsstrahlung from ultrarelativistic electrons in homogeneous condensed matter. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 145–149 (10 February 1996)     

Diffusion rate in diamond growth

Conclusions Equations were established that relate the growth rate of diamond crystals in the region of its thermodynamic stability to the synthesis time.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2647–2649, November, 1978.     

Studies of the microstructure of a superconducting Nb<Subscript>3</Subscript>Sn-Band obtained from (Cu/Nb)/Cu12Sn nanocomposite

A multilayer layer from the superconducting compound Nb₃Sn was obtained by the thermal treatment of composite (Cu/Nb)/Cu12Sn conductor consisting of Cu-12% Sn and Cu/Nb interlayers consisting in turn of nanosized copper and niobium layers. The conductor was coated with copper from the outside, which served as a stabilizer. The microstructure of the cross section of the composite band in dependence on the volume ratio of Cu/Nb and bronze interlayers and the microstructure of the Cu/Nb interlayers themselves in dependence on the annealing temperature were investigated. The optimum ratio of composite components was as follows: t _Nb N _Nb ≈ 0.288t _CuSn N _CuSn, where t and N are the thickness and number of the niobium and bronze layers, respectively. Trying to maintain the optimum design of the conductor forced us to increase the bronze volume content relative to the content of Cu/Nb interlayers, which had a negative impact on the composite microstructure. This resulted in disruptions of Cu/Nb interlayers. A technique has been developed for producing the (Cu/Nb)/Cu12Sn composite as a precursor to the band from the Nb₃Sn compound with allowance for the first experiment’s shortcomings.     

Parametric X Radiation from Electrons in Mosaic Crystals

A simple model for calculating the contribution of diffraction of actual photons to the measured spectrum of parametric x radiation (PXR) from relativistic electrons in mosaic crystals is suggested. It is shown that the diffraction of real photons of bremsstrahlung and transition radiation in mosaic crystals whose thickness t is about 0.01 of the radiation length makes a significant contribution to the measurable emission spectrum. The spectra and angular distributions of PXR from electrons with energies 500 and 900 MeV have been measured in mosaic pyrolytic graphite crystals. It is demonstrated that with consideration of diffraction of actual photons in the mosaic crystal, including diffraction of PXR photons, all experimental data presently available agree well with the results of calculations for the suggested model.     

The number of photons emitted by a channeled electron

A discussion is presented of the influence of photon multiplicity in the emission from channeled electrons on the radiation spectrum measured by a total-absorption spectrometric device. It is shown that as the maximum in the spectrum shifts with increasing crystal thickness, in the absence of further information it is impossible to determine the multiplicity of the emission. A method is proposed for determining the presence of multiple emission from channeled electrons with a total-absorption spectrometer by using an absorber covering a specified portion of the -ray aperture. The presence of multiplicity is identified in emission from channeled electrons with energy E₀=900 MeV in a tungsten single crystal of 1.18 mm. Previously the presence of multiplicity in the radiation from channeled electrons had been detected for electron energies above 4.5 GeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 88–105, June, 1991.     

Experimental study of the albedo of a beam of γ rays produced by ultrarelativistic electrons

A study has been carried out of the spectral dependence of -radiation scattered from targets irradiated with beams of rays produced by relativistic electrons in crystals. It is shown that the change in the spectral composition of the beam of rays incident on the target changes considerably the spectral properties of the scattered radiation. The spectra of the scattered radiation are studied as a function of the thickness and atomic number of the scatterer. It is shown that the atomic number of the scattering material can be determined from the ratio of the spectral components of the scattered radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 106–119, June, 1991.     

Properties of coherent bremsstrahlung from electrons in thick single crystals

A technique for calculating the frequency and polarization of the coherent bremsstrahlung from relativistic electrons in single crystals of arbitrary thickness is proposed and implemented. It accurately includes multiple scattering of the emitting particles and the angular distribution and collimation of the radiation. The spectral properties of the collimated beam of radiation from electrons with energies of 900 MeV in thick (0.1 r.l.) single crystals of diamond, silicon, and tungsten are compared with the calculations. When the radiation is tightly collimated the dependence of the frequency and polarization properties of the radiation on the multiple scattering of the emitting particles in the crystals becomes weaker.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 21–43, June, 1991.     

Intermolecular Complexes of Active Oxygen Forms with Amino Acids. A Theoretical Study

Ab initio quantum-chemical calculations were used to examine the thermodynamic aspects of binding of molecular oxygen and the radical anion O₂ ^·- with certain amino acids. It was shown that amino acids form no stable systems with molecular oxygen but form thermodynamically stable complexes with the superoxide radical anion.