Energy Distributions of High Energy Primary Knock-ons Produced by Fission Fragments

The limits of validity of some approximations for the problem of collisions between fission fragments and lattice atoms in aluminium, gold and uranium are determined on the basis of Bohr's criteria. The Rutherford approximation is found to be valid for the wide range of energies of fission fragments. Numerical calculations are made of the mean free paths of fission fragments for producing high energy knock-ons and the energy distributions of high energy primary knock-ons. Results for the degradation of energies from the initial values near 100 MeV to ∼1 or ∼0.1 MeV are presented.