Study of the (n,xn) and (n,f) reactions for 238U

In the fast-neutron induced reactions on actinides every process is closely linked. This is particularly true for (n,xn) and fission reactions which are the most probable processes in the energy domain considered for this experiment (6-30 MeV). The proposed experiment has two goals, the first one is to measure accurately the (n,xn) reactions cross-sections, and the second one is to study the particle emissions in fission. Accurate measurements of (n,xn) cross sections deeply challenge the validity of the various reaction mechanisms models and will help to improve them. For the fission process we will measure the prompt neutron multiplicities, and the total prompt g-ray energy. Neutron multiplicities are very important for applications and are hardly reproduced by theoretical model. Concerning the total g-ray energy it is strongly related to the angular momentum generated at scission, and this mechanism is still poorly known. These two purposes can be attained at the same time thanks to a unique experimental setup composed of the new SCONE detector, and a multi-plate fission chamber. We aim to perform a first experiment on uranium 238, since the (n,2n) cross-section was accurately measured through the activation technique, but direct neutron counting measurements disagree. Moreover we will see that such a multi-process measurement is interesting from a theoretical point of view. Hence the proposed experiment can be considered as a commissioning experiment for a program on actinides, but also as an important and challenging experiment.