A Novel Method for Kinematic Neutron-Energy Compensation in Fast-Neutron Spectroscopy

Fast-neutron-energy measurements are essential for nuclear particle research and dosimetry. However, such measurements are challenging due to the low interaction probability of fast neutrons with the matter, given their small cross section for scattering and absorption compared to thermal neutrons, as well as their zero charge. Traditional neutron-energy measurement methods have limitations related to the distance and detector size. Therefore, this study proposes a novel kinematic neutron-energy compensation method that measures neutron scattering using the first detector and directly captures fast neutrons using the second detector. The scattering and post-scattering energies of neutrons are measured and used to reconstruct the neutron energy, enabling more accurate measurements of high-energy monoenergetic neutrons. This method is less sensitive to the energy and angle distribution of neutrons as they interact with the first detector and scatter toward the second detector. The energy deposited in the first detector is measured, while the scattered fast-neutron energy is determined through nuclear reactions within the second detector, enabling event-by-event compensation in energy reconstruction. Therefore, the system is not sensitive to the distance between detectors or the solid angle determined by the detector size. The performance of the system is verified using EJ-309 liquid and 7Li-enriched Cs2LiYCl6:Ce3+ scintillators. In addition, at Korea Research Institute of Standards and Science (KRISS), 14.8-MeV monoenergetic neutrons were used to characterize the proposed method, achieving an energy resolution of 2.8% full-width at half-maximum (FWHM) for measurements and energy reconstruction.