Properties of prompt-fissionγrays

Abstract

In a Monte-Carlo Hauser-Feshbach statistical framework, we describe spectra, average multiplicities, average energy and multiplicity distributions of the prompt γ rays produced in the thermal neutron-induced fission of 235 U and 239 Pu, and the spontaneous fission of 252 Cf. Comparisons against recent experimental data show reasonable agreement in all cases investigated, after adjustment of the initial spin distribution in the fission fragments. In particular, when we include in the calculation the Doppler broadening we obtain a qualitatively good description of the measured low-energy spectra, where contributions from collective discrete transitions in specific fragments can be identified. At higher energies, both the calculated neutron and γ-ray spectra are softer than experimental data. The impact of selected model parameters on the prompt neutron and γ-ray spectra is analyzed. Finally, we present prompt γ spectrum and multiplicity distribution for the neutron-induced fission of 235 U for 5.5 MeV neutron incident energy, just below the threshold for second-chance fission.

Energy dependence of the promptγ-ray emission from the(d,p)-induced fission ofU*Rose1, Zeiser2, Wilson3 et al. 2017Phys. Rev. C121110View full textAdd to dashboardCite

“…One question deals with the de-excitation of nuclei through the emission of neutrons and γ-rays. The theoretical description of the de-excitation of neutron-rich isotopes, as being produced in neutron-induced fission, shows significant deficits in describing the neutron and γ-ray spectral shape [8]. To some extent this deficiency seems to be related to a limited understanding of the competing process of prompt neutron and γ emission.…”

“…Prompt fission γ-ray spectral (PFGS) data, measured as a function of excitation energy of the compound nucleus may provide important information to benchmark different models, allowing eventually arrival at a consistent description of prompt fission neutron and γ-ray emission. Furthermore, PFGs are certainly among the most sensitive observables for studying angular momentum generation in fission [8,9].…”

“…Prompt fission γ-rays (PFG) are emitted, typically within a few nanoseconds of scission of the fragments; about 70% of the prompt PFGs are emitted within 60 ps, and about 95% within 3 ns [7]. PFGs are one of the least understood parts of the fission process [8].…”

Future research program on prompt $\gamma$ -ray emission in nuclear fission

“…Nevertheless, since there is an important mutual stimulation between theory or modeling and experiment, we would like to mention here briefly ongoing work on the modeling and theoretical description of prompt fission γ-ray emission. Without claiming of being complete we mention work recently performed at the Los Alamos National Laboratory (CGMF [62][63][64][65]), the Lawrence Livermore National Laboratory (FREYA [66][67][68]) and the CEA Cadarache (FIFRELIN [69][70][71][72]). Whereas FREYA uses analytical expressions based on Weisskopf's statistical theory to describe neutron and γ-ray emission all other models are based essentially on the Monte Carlo Hauser-Feshbach statistical theory.…”

Prompt fissionγ-ray characteristics from neutron-induced fission on 239Pu and the time-dependence of prompt-γray emission

“…The advances made in recent editions of various fission models presently on the market [3][4][5][6][7][8][9] require precise experimental data on prompt fission neutron and γ-ray emission as input parameters. For example multiplicity, average energy per particle and total dissipated energy per fission, preferably as function of fission-fragment mass and total kinetic energy, are key input to benchmark nuclear fission models attempting to describe the competition between prompt neutron and γ-ray emission.…”