Energy dependence of the prompt ${\gamma}$-ray emission from the $(d,p)$-induced fission of $^{234}\mathrm{U}^{*}$ and $^{240}\mathrm{Pu}^{*}$

TL;DR

This study measures prompt gamma-ray emission from fission of uranium and plutonium isotopes as a function of excitation energy, revealing minimal spectral changes and comparing results with models and neutron-induced fission data.

Contribution

First measurement of prompt gamma-ray emission characteristics as a function of excitation energy in (d,p)-induced fission of $^{234}$U* and $^{240}$Pu*.

Findings

Gamma-ray spectra show no significant change with excitation energy above the fission barrier.

Results are consistent with model calculations using the GEF code.

Comparison with thermal neutron fission data highlights possible differences due to reaction type.

Abstract

Prompt fission $\gamma$-rays are responsible for approximately 5\% of the total energy released in fission, and therefore important to understand when modelling nuclear reactors. In this work we present prompt $\gamma$-ray emission characteristics in fission, for the first time as a function of the nuclear excitation energy of the fissioning system. Emitted $\gamma$-ray spectra were measured, and $\gamma$-ray multiplicities and average and total $\gamma$ energies per fission were determined for the $^{233}$U(d,pf) reaction for excitation energies between 4.8 and 10 MeV, and for the $^{239}$Pu(d,pf) reaction between 4.5 and 9 MeV. The spectral characteristics show no significant change as a function of excitation energy above the fission barrier, despite the fact that an extra $\sim$5 MeV of energy is potentially available in the excited fragments for $\gamma$-decay. The measured results are compared to model calculations made for prompt $\gamma$-ray emission with the fission model code GEF. Further comparison with previously obtained results from thermal neutron induced fission is made to characterize possible differences arising from using the surrogate (d,p) reaction.