PRODUCT YIELDS FOR THE PHOTOFISSION OF 239Pu WITH BREMSTRAHLUNG AT 17.5 MeV BOUNDARY ENERGY

The values of relative cumulative yields of 12 products (85mKr, 91mY, 92Sr, 97Zr, 99Mo, 105Ru, 133I, 134I, 135I, 138Cs, 139Ba, 142La, 143Ce) of the 239Pu photofission was measured at a maximum bremsstrahlung energy of 17.5 MeV (av-erage excitation energy ~ 12.03 MeV). 239Pu photofission reaction was stimulated on the electron accelerator of the Institute of Electron Physics NAS of Ukraine – M-30 microtron to simulate the spectra of bremsstrahlung’s photons, secondary electrons, and photoneutrons that hit the 239Pu target, the GEANT4 code was used. The input of accom-panying nuclear reactions to the yield of 239Pu photofission products for the given experimental parameters was also evaluating. The obtained experimental data of the yields of products 239Pu photofission were compared with the program codes GEF and Talys1.9.5 simulations.

GAMMA–ALPHA REACTIONS IN THE LIGHT NUCLEI OF NUCLEAR EMULSIONS

Ilford E.1 nuclear emulsions were loaded with various amounts of glycerine to vary the content of carbon and of oxygen, and were then irradiated in the beam of the University of Saskatchewan betatron. The numbers of single alpha-particle tracks and of four-pronged alpha-particle stars were correlated to the oxygen content of the plates and the number of three-pronged stars to the carbon content. The yields for the reactions O16(γ, α)C12, O16(γ, 4α), and C12(γ, 3α) for bremsstrahlung of 24-Mev maximum energy were found without confusion with reactions in other nuclides of the emulsion and without having to rely on momentum balances for identification of the events. It was shown that the method of identification of 016(γ, α)C12 events by the measurement of the track of the C12 was not reliable. The large number of alpha tracks in the energy range 4 to 5 Mev, few of which showed a C12 track, was shown to be due largely to reactions in O16. It was also possible, by irradiating emulsions at 17- and at 24-Mev maximum bremsstrahlung energy, to find the energy levels in O16 and in C12 through which the reactions passed.

PHOTONEUTRON REACTIONS IN G12 AND O16

Absolute yields of the reactions C12(γ,n)C11 and O16(γ,n)O15 have been determined at 22-Mev maximum bremsstrahlung energy using the University of Saskatchewan 24-Mev betatron. For the reaction C12(γ,n)C11 a yield curve from threshold to 24 Mev has been obtained and the cross-section curve for the reaction computed. A thorough comparison with other results has been made.

THE ANGULAR DISTRIBUTION OF PHOTOFISSION FRAGMENTS

Angular distributions of photofission fragments relative to the photon beam have been measured as a function of maximum bremsstrahlung energy in the range 6–20 Mev. The nuclides U-233, U-235, Np-237, Pu-239, and Am-241 give an isotropic distribution at all energies studied. The nuclides Th-232, U-234, U-236, U-238, and Pu-240 give anisotropic distributions which can be described by an equation of the form W(θ) = 1 + α sin2 θ where θ is the angle between fragment and beam. The degree of anisotropy is large at low energy and falls rapidly as the energy is increased. At a given energy Th-232 has the greatest degree of anisotropy and Pu-240 the least.

Radiative corrections to the scattering of electrons and positrons by electrons

The e 6 corrections to the Moller formula for the scattering of electrons by electrons and the Bhabha formula for the scattering of positrons by electrons, arising from the interaction of the particles with virtual photons, are formulated using the Feynman-Dyson techniques. After removing ultra-violet divergences by mass and charge renormalization the cross-section still suffers from a logarithmic infra-red divergence. This is cancelled by adding on the cross-section for the production of a single real photon of low energy during the collision. The result is evaluated assuming that the maximum bremsstrahlung energy radiated is small compared with the rest energy of the electron, as viewed from the laboratory frame. Non-relativistic and extreme relativistic approximations to the formulae are presented, together with the results of exact calculations for a laboratory energy of 20 mc 2 .