Total kinetic energy release in the fast neutron-induced fission of 237Np

The total kinetic energy (TKE) in the fast neutron induced fission of 237Np was measured for neutron energies from En = 2.6 - 100 MeV at the LANSCE-WNR facility. The post TKE release decreases non-linearly with increasing incident neutron energy and can be represented as TKE(MeV) = (174.38 +- 0.72) - (5.11 +- 0.5821) log10 En for En > 1 MeV. Analysis of the fragment mass distributions indicates that the decrease in TKE with increasing En is a consequence of two factors; shell effects fade out at high excitation energies, resulting in the increasing occurrence of symmetric fission, and TKEasym decreases rapidly at high En.