Eur. Phys. J. A (2020) 56: 297
https://doi.org/10.1140/epja/s10050-020-00295-6

Regular Article – Experimental Physics

Total kinetic energy and mass yields from the fast neutron-induced fission of ${}^{239}\text{Pu}$

¹ Department of Chemistry, Oregon State University, Corvallis, OR, USA
² P-27, Physics Division, Los Alamos National Lab, Los Alamos, NM, USA

^d lovelanw@onid.orst.edu

Received: 18 September 2020
Accepted: 18 October 2020
Published online: 26 November 2020

Abstract

The total kinetic energy (TKE) release in fission is an important observable, constituting over 80% of the energy released in fission (${\text{E}}_f\approx 200\text{MeV}$). While the TKE release in the ${}^{239}\text{Pu}$(n,f) reaction was previously measured up to 50 MeV incident neutron energy (${\text{E}}_n$), there were features in TKE release at the highest values of ${\text{E}}_n$ that were puzzling. There was a marked flattening of TKE release from ${\text{E}}_n=30$ to 50 MeV, in disagreement with the clearly decreasing TKE observed from ${\text{E}}_n=0.5$ to 30 MeV. To verify and clarify this trend, TKE measurements at higher values of ${\text{E}}_n$ were made. We present absolute measurements of TKE release in ${}^{239}\text{Pu}$(n,f) from ${\text{E}}_n=2.4$ to 100 MeV. We used silicon PIN detectors to measure the fragment energies and deduce mass-yield curves using the 2E-method. We also discuss fission asymmetry and the relationships between approximate fission fragment mass and distortion.