Development of a transportable neutron imager for localization of radioactive sources

Locating radioactive hot spots presents a significant challenge for the nuclear industry and security applications, such as waste management, decommissioning, radiation protection, and the management of nuclear accidents. The detection of fast-neutron emissions offers an alternative technique to gamma imaging for verifying the location of radioactive materials, particularly in cases where gamma imagers face challenges in detection. In this study, we present the performance of a prototype gamma-neutron imaging system based on a custom-fabricated plastic scintillator, designed to effectively discriminate between signals from gamma radiation, fast neutrons, and thermal neutrons. We conducted Geant4 simulations to investigate neutron interactions within the plastic scintillator and compared the simulation results with experimental data. Additionally, we performed experiments on the prototype using a proton beam at the CYRCé facility at IPHC, utilizing a CMOS Monolithic Active Pixel Sensor (MAPS) called MIMOSIS to analyze the beam profile. Through these efforts, we examined neutron interactions with our scintillator, validated the prototype's imaging capabilities under proton beam exposure, and conducted a calibration study of its energy response.