Fission of heavy nuclei by linearly polarized photons

Analysing power Σ data from photofission of ²³²Th, ²³³U, ²³5U, ²³⁶U, ²³⁸U at the region of giant resonance have been measured using linearly polarized photons. The polarized photons were obtained by plane channelling of electrons in a silicon single crystal. The analysing power Σ dependence of the mass number of even-even nucleus has been discovered. Comparison of the analysing power Σ values with the data from other experiments with both polarized and unpolarized photon beams was made. It is shown that the analysing power Σ values agree with the modern knowledge of E1 transitions but cannot be explain by domination any one of them. It is supposed that analysing power Σ is very sensitive to different relative inner and outer fission barrier heights and this affects on Σ values for even-even nuclei with the same Z

Linear polarization of photons produced by the electrons moving along the crystallographic plane in a silicon crystal

We present the results of the polarization and intensity measurements versus photon energy Eg=5-35 MeV for the photon beam produced by the electrons with the energies 1.2 and 1.5 GeV moving in the silicon crystal 500 and 290 mm thick along the (110) plane. The comparison with results of another research group and theoretical calculation indicates the qualitative agreement. The correlation in the shape of the radiation intensity spectrum and its polarization energy dependence is observed

Quasi Free 238U (e,e'f)-Cross Section in Macroscopic-Microscopic Approach

We present the result of a theoretical study of inclusive quasi free electrofission of $^{238}$U. The off-shell $$cross sections for the quasi free reaction stage have been calculated within the Plane Wave Impulse Approximation (PWIA), using a Macroscopic -Microscopic description of the proton and neutron single particle momentum distributions. Electron wave function distortion corrections were included using the effective momentum approximation, and the Final State Interaction (FSI) effects were calculated using an optical potential. The fissility for the proton single hole excited states of the residual nucleus $^{237}$Pa was calculated both without and with contributions of the pre-equilibrium emission of the particles. The fissility for $^{237,238}U$ residual nuclei was calculated within the compound nucleus model. The $(e,e^{\prime}f)-$cross sections thus obtained were compared with available experimental data.Comment: 26 pages, 7 figure

Incoherent X-radiation produced by relativistic electrons in crystals

Differential and integral features of incoherent X-radiation, induced by relativistic electrons in crystals, are studied for observation angles $\theta _{\gamma }$ several times greater than $\gamma ^{-1}$, where $\gamma$ is the projectile Lorentz factor. The existence of sharp maxima and a minimum of the five-folded incoherent differential cross-section as a function of the final electron angles, and a dip minimum when the cross-section is taken as a function of the photon energies, is demonstrated. At near backward observation angles the three-folded cross-section shows a maximum in the region of several keV photon energies. The obtained results allow us to optimize the conditions for coincidence experiments, minimizing the incoherent contribution to the total radiation yield, and helping to analyse results of finite-size detector experiments with crystal targets