Simulation design and performance evaluation of the wide-energy range gamma-ray imaging detectors

Compton imaging is a technology to detect nuclear radiation intuitively. Due to the limitations of detector volume and types of imaging events, the energy range of traditional Compton imaging is usually 0.3–3 MeV. It is difficult to consider the application of prompt γ imaging with an energy distribution of 3–7 MeV on the basis of natural nuclide imaging. One of the important development directions to expand the application fields of nuclear radiation detection and imaging is gamma imaging with a wide-energy range covering 0.3–7 MeV. A three-layer detector structure based on double scattering is a potential implementation scheme in which the design and construction of the detector are the foundation and core. Considering the system cost and expansion flexibility, a silicon photomultiplier (SiPM) array and a gadolinium gallium aluminum garnet (GAGG:Ce) array are selected as detector materials in this paper. According to the requirements of imaging events for three-layer detectors, the characteristics of interaction events in each layer of the detector are analyzed. A simulation model including optical parameters of materials is established on the Geant4 Monte-Carlo simulation platform. The position maps of detectors and statistical results of interaction events in detectors with different geometric parameters are compared by setting up the physical process and two information extraction methods. According to the simulation design, two kinds of SiPM detector modules are composed of a GAGG array with a pixel number of 15×15, pixel size of 3.2 mm× 3.2 mm, and thickness of 3 and 10 mm, respectively. The thickness of the light guide between the GAGG and SiPM arrays is 1.25 mm. The performance of two detector modules is evaluated based on the electronic readout system. The results show that the scatterer detector with a thickness of 3 mm and the absorber detector with a thickness of 10 mm can clearly distinguish the interaction position on 15×15 pixels. The average peak-to-valley ratio is 9.77 and 11.85, respectively. The average energy resolution of all pixels at 662 keV is 7.21% and 8.35%, respectively. In this paper, both detectors show good resolution capacities for interaction position and deposited energy. The developed simulation model, analysis results, and detector modules provide an important basis for the construction of a three-layer detector system and lay a scientific and technological foundation for the realization of wide-energy range γ imaging. © 2024 Chinese Academy of Sciences. All rights reserved.