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

TL;DR

This study measures the total kinetic energy released during fast neutron-induced fission of 237Np across a wide energy range, revealing a non-linear decrease linked to shell effects and fission symmetry.

Contribution

It provides the first detailed measurement of TKE in 237Np fission for neutron energies from 2.6 to 100 MeV, and models the energy dependence with a logarithmic relation.

Findings

TKE decreases non-linearly with neutron energy

Shell effects fade at high excitation energies

Symmetric fission becomes more frequent at high energies

Abstract

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.