Characterization of a Fast Neutron Irradiation Facility Using a Stilbene Scintillation Detector

Abstract

This paper describes the characterization of a fast neutron facility located at Legnaro National Laboratories’ Van de Graaff CN accelerator. The neutron flux is produced by the 9 Be( p , xn ) reactions, generated by a beryllium thick target bombarded with 5-MeV protons. An iterative unfolding algorithm combined with a pulse shape discrimination technique were used to obtain the energy distributions of the emitted neutrons at different angles and to compute the absolute neutron flux as a function of the proton current. With a proton current of 180 nA and a distance of 5 cm from the emission point, a maximum neutron flux of 2.6 × 10 6 cm−2 s−1 ( ± 15%) was obtained. The gamma-ray component made up around 32% of the total radiation field. The measurements were taken with a Stilbene scintillation detector, therefore a comprehensive study of the detector was also performed, including energy calibration, determination of the proton light output function, and intrinsic neutron detection efficiency. Based on the results and the capabilities of the Stilbene detector, it can be concluded that this detector is suitable for fast neutron flux characterization. It enables quick measurements and real-time monitoring of the neutron field.