Energy dependence of prompt fissions neutron multiplicity in the 239Pu(n,f) reaction
P. Marini, Julien Taı̈eb, Denise Neudecker, G. Bélier, A. Chatillon, D. Etasse, B. Laurent, P. Morfouace, B. Morillon, M. Devlin, J.A. Gómez, R. C. Haight, Keegan Kelly, J. M. O’Donnell
Abstract
Accurate multiplicities of prompt fission neutrons emitted in neutron-induced\nfission on a large energy range are essential for fundamental and applied\nnuclear physics. Measuring them to high precision for radioactive fissioning\nnuclides remains, however, an experimental challenge. In this work, the average\nprompt-neutron multiplicity emitted in the 239Pu(n,f) reaction was extracted as\na function of the incident-neutron energy, over the range 1-700~MeV, with a\nnovel technique, which allowed to minimize and correct for the main sources of\nbias and thus achieve unprecedented precision.\n At low energies, our data validate for the first time the ENDF/B-VIII.0\nnuclear data evaluation with an independent measurement and reduce the\nevaluated uncertainty by up to $60\\%$. This work opens up the possibility of\nprecisely measuring prompt fission neutron multiplicities on highly radioactive\nnuclei relevant for an essential component of energy production world-wide.\n