THE ANGULAR DISTRIBUTION OF PHOTOFISSION FRAGMENTS

Abstract

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.