High-Energy Fission ofU238

Abstract

The results of a study of the thick-target recoil properties of fission products from the 450-MeV proton fission of ${\mathrm{U}}^{238}$ are reported here. The average kinetic energy, the average cascade deposition energy, and the average anisotropy of an isolated product are calculated from the recoil results. The characteristics of the most probable fission products, and of the primary fragments leading to them, are then calculated. The average total kinetic energy of the primary fragments is found to be 163\ifmmode\pm\else\textpm\fi{}8 MeV and the average separation of their charge centers at the scission point is 18.4\ifmmode\pm\else\textpm\fi{}0.5 F. The angular distribution of the fission fragments is somewhat anisotropic, favoring perpendicular emission of fragments for low cascade deposition energies and forward-backward emission for high deposition energies. The momentum-deposition energy relation obtained from the Monte Carlo intranuclear cascade calculations leads to an average cascade deposition energy of 123 MeV for the fission process, somewhat lower than the value 147 MeV calculated for all cascade nuclei. The cascade deposition energy, calculated from recoil results, for formation of a specific nuclide agrees with that determined from an analysis of its excitation function to about 20%.