ANISOTROPY IN THE SCATTERING OF THERMAL-NEUTRONS IN CRYSTALLINE MODERATORS BERYLLIUM

To study the anisotropy in scattering of thermal neutrons in beryllium, the authors calculated elastic as well as inelastic differential cross sections. Anisotropy in elastic scattering is studied by replacing the delta function by a Gaussian function of suitable width. To study the anisotropy in inelastic scattering, they have calculated one-phonon coherent inelastic differential cross sections. The differential cross sections for the one- and two-phonon processes have also been calculated in the incoherent approximation. They have also expanded in angle dependence of cross section in terms of the Legendre polynomials. Using the above differential cross sections, the intensity of scattered neutrons in various angular directions has been calculated, and the results have been compared with the corresponding observed results of Aizawa et al. Calculated results are found in good agreement with the corresponding observed results. The authors have investigated the effect of anisotropy in scattering on steady-state angular spectra inside small beryllium assemblies.