Prompt Neutrons from Fission ofU238Induced by 12-MeV Protons

The number of prompt neutrons and their average energies in correlation with fragment mass and kinetic energy have been measured directly for fission induced in ${\mathrm{U}}^{238}$ by 12-MeV protons. The sawtooth behavior evident for the average number of neutrons as a function of fragment mass (similar to the behavior in thermal neutron fission of ${\mathrm{U}}^{233}$, ${\mathrm{U}}^{235}$, and ${\mathrm{Pu}}^{239}$) disappears for events of low total kinetic energy.