Recently, global concerns regarding the illicit transportation and trafficking of nuclear materials and other radioactive sources have increased, leading to increased demands for efficient and rapid security and non-proliferation technologies. The International Atomic Energy Agency's Incident and Trafficking Database has reported 3 235 confirmed incidents involving nuclear and other radioactive materials out of regulatory control from 1993 to 2017. Of these incidents, 278 are associated with trafficking or malicious use of materials such as highly enriched uranium, plutonium, and plutonium-beryllium neutron sources. Therefore, developing depth-of-interaction detector for neutrons and gamma rays is important for effective control of nuclear and radiation materials at national and international cross points such as borders, ports, and airports.

This study aims to design a depth-of-interaction detector for neutrons and gamma rays and characterize its performance.

Hereby, an EJ276 plastic scintillator (Φ3 cm× 15 cm) coupled with two silicon photomultipliers (SiPMs) in both sides was designed as a depth-of-interaction detector for neutrons and gamma rays. The short gate time was optimized to achieve better neutron/gamma-ray discrimination, and the reaction position was determined based on the amplitude ratio and time of flight (TOF) difference between signals from two sides. Finally, Am-Be neutron source and ¹³⁷Cs γ source were applied to detector parameter optimization and resolution calibration for performance characterization.

Experimental results demonstrate that good consistency in the detection efficiency of the detector at different incident positions, where the resolution of the one-dimensional reaction position is approximately 4.4 cm.

The designed depth-of-interaction detector can be used toreplace detector arrays in neutron scatter cameras and coded-aperture imagers to reduce costs and system complexity.