Kinetic-energy distributions and the correlation of anisotropy and asymmetry in the 4-MeV neutron-induced fission of U²³⁵

Abstract

The kinetic-energy distributions and the correlation of the angular anisotropy and the mass asymmetry of the fission fragments have been determined in the fission of U²³⁵ induced by 4-MeV neutrons. The kinetic energies of the pair of fragments emitted parallel and perpendicular to the incident beam direction are measured by solid-state detectors and recorded by a three-dimensional analog-to-digital converter incorporating a printout arrangement. The observed variation of the total kinetic energy E̅_k and the mean-square deviation σ_Ek² are found to be different from that observed for the case of thermal fission. For the near-symmetric fragments the total-kinetic-energy distributions show a small peak at an energy of about 125 MeV in addition to the main peak at 163 MeV. The anisotropy has been found to increase with the asymmetry in the region of mass ratios 1.2 to 1.7. The different possibilities leading to the observed dependence of the anisotropy on the asymmetry are discussed.