Prompt fission neutron multiplicity in the Resolved Resonance Region of 239Pu

This thesis investigates the role of the (n,gf) process on the number of prompt neutrons emitted per fission (multiplicity “nubar”) in the resolved resonance region of Pu-239 (from 0.3 to 100 eV). The emission of gamma rays prior to fission may explain the observed reduction in nubar in this energy region. In a first step, time-of-flight experiments are to be carried out at JRC's GELINA facility in Geel, Belgium. A second step of the thesis will be to use the FIFRELIN code developed in our Cadarache laboratory to simulate fission events. For resonances with a strong (n,gf) component, the gamma emitted before fission should significantly modify the spectrum of prompt fission gammas emitted by the fragments, due to a decrease in the excitation energy in the system. This phenomenon of gamma emission before fission is not yet taken into account in the FIFRELIN code, the student will have to implement a model to do so. A simple solution would be to model the process in two stages: emission of a gamma by the compound nucleus (model already implemented) and then fission of the residual nucleus (model also implemented). As part of this research work, the doctoral student will develop competence in theoretical and experimental nuclear physics