(α+⁹Be) neutron production cross sections trends to improve neutron spectrum calculations using MCMC techniques

This work presents different methodologies to estimate trends on α + 9 Be neutron production cross sections to enhance neutron spectrum calculation of alpha beryllium sources. The simulation of an Am-Be source and its comparison with several experimental references are presented. This study highlights the contribution of neutron angular distributions to reduce the gap between experimental and calculated spectra. The use of EXFOR angular distributions shows interesting results for outgoing neutrons between 5 MeV and 10 MeV. Cross sections are re-estimated using a Markov Chain Monte Carlo algorithm. The global methodology is based on a coupling between a Geant4 tool, SaG4n, and a Metropolis-Hastings algorithm. The cross sections adjustments suggest the mis-estimation of the ( α , α + n ) reaction and partial ( α , n i ) reactions. In this context, two ways of modeling cross sections are compared: one using Bayesian inference, and one using Gaussian processes.