Prompt-fission $\gamma$-ray spectral characteristics from $^{239}$Pu($_ {th}$,f)

International audienceIn this paper we present new results for prompt fission γ-ray spectral characteristics from the thermal neutron induced fission of Pu*240. The measured spectra were unfolded by using the detectors' response functions, simulated with geant4. We obtained in average per fission a γ-ray multiplicity M¯γ=(7.35±0.12), a mean photon energy ε¯γ=(0.85±0.02) MeV, and an average total energy released in fission E¯γ,tot=(6.27±0.11) MeV. Our results are in good agreement with historical data measured in the 1970s by Verbinski et al. and results from recent calculations in the framework of Monte Carlo Hauser–Feshbach models. Our measured average total energy is slightly smaller than the one deduced previously and present in evaluated data. From this we conclude that the Pu239(nth,f) reaction may be ruled out as possible source of γ heating underestimation, when compared with benchmark calculations based on existing nuclear data