Study of a compact NRA system : report prepared as part of the INFN - JRC collaboration agreement

A compact system for Neutron Resonance Analysis has been studied based on results of simulations. The influence of the moderator characteristics of the neutron producing target on both the neutron emission spectrum and the time-of-flight response functions has been investigated. Results obtained with different moderator geometries and materials have been compared. In addition, the transmission through a complex sample was simulated to verify the impact of the moderator thickness and pulse width on the observed resonance transmission profiles. Results have been validated by a comparison with experimental transmission data obtained from measurements at a 10 m transmission station of GELINA. The results of this study reveal that the response functions and the energy dependence of the neutron spectrum are almost independent of the energy of initial neutrons. The absolute intensity decreases with increasing initial neutron energy. The best results are obtained when the face of the moderator viewing the flight path is flat. As expected, the moderator geometry, material and thickness have a strong impact on the response functions and on both the energy dependence and absolute intensity of the neutron spectrum. Schemes to optimise the moderator thickness and initial pulse width are presented.