Neutron-Induced Scintillation in Organics

Sammanfattning: Neutrons are widely used as probes of matter to study materials in a broad range of fields from physics, chemistry and medicine to material sciences.Any application utilizing neutrons needs to employ a well-understood and optimized neutron-detector system. This thesis is centered on fundamental aspects of neutron-detector development, including the establishment of the Source Testing Facility at Lund University, experimental methods for the in-depth characterization of scintillator-based neutron detectors and analytical and computational methods for the precise interpretation of results. It focuses on the response of liquid organic scintillators to fast-neutron and gamma-ray irradiations, specifically for NE~213A, EJ~305, EJ~331 and EJ~321P.A simulation-based method for detector calibration was developed which allowed for the use of polyenergetic gamma-ray sources in this low energy-resolution environment. With an actinide/beryllium neutron source and a time-of-flight setup, beams of energy-tagged neutrons were used to study the energy-dependent behaviour of the intrinsic pulse-shape of NE~213A and EJ~305 scintillators. The results demonstrated the advantages of the neutron-tagging method and how the combination of neutron tagging and pulse-shape discrimination can give deeper insight into backgrounds resulting from inelastic neutron scattering. A comprehensive characterization of the neutron scintillation-light yield for NE~213A, EJ~305, EJ~331 and EJ~321P was also performed.It employed the simulation-based calibrations to confirm existing light-yield parametrizations for NE~213A and EJ~305, and resulted in light-yield parametrizations for EJ~331 and EJ~321P extracted for the first time from data.In addition to the development of a simulation-based framework for the study of neutron-induced scintillation in organic scintillators, the methods and results presented in this thesis lay the foundation for future source-based neutron-tagging efforts and scintillator-detector research and development.