Design of a Dual-Scintillator Anti-Coincidence Detection System for Enhanced Energy Resolution and Background Suppression in Mixed-Field Low-Energy Gamma Spectroscopy

This work proposes a novel dual-scintillator anti-coincidence detection system consisting of a front-layer LYSO auxiliary scintillator and a rear 1”×1” LaBr3(Ce) main detector, designed for high-resolution low-energy gamma-ray spectroscopy in mixed-field environments by mitigating Compton scattering, charged particle interference, and intrinsic background. Geant4 simulations identified that a 3 mm-thick, 68 mm-diameter LYSO layer achieves the optimal overall system performance by suppressing 91.50% of charged-particle interference and improving the peak-to-Compton ratio (PCR) by 42.4% for137Cs and by 45.6% under “137Cs +90Sr” mixed-field conditions compared to the standalone LaBr3(Ce) detector. Experimental validation with multiple gamma sources (0.511-1.33 MeV) and mixed β-γ radiation fields confirmed the simulation results. With an optimized 130 ns anti-coincidence (AC) time window, the system exhibited improved spectral purity and reliable Gaussian fits, the energy resolution (ER) at 662keV improved to 3.26%, and further to 3.21% under mixed-field conditions. In the challenging “137Cs +90Sr” environment, the anti-coincidence detection system enhanced the PCR to 2.0696 and the Peak-to-Total Ratio (PTR) to 0.4492, corresponding to a Peak-to-Compton Suppression Factor (PCSF) of 9.87 and a Peak-to-Total Suppression Factor (PTSF) of 19.79. Moreover, the intrinsic176Lu activity in the LYSO crystal, typically a source of interference, was advantageously utilized for in-situ self-calibration, enabling accurate background subtraction and stable energy alignment, which ensured reliable PCR and PTR determination. The proposed LYSO-LaBr3(Ce) dual-scintillator anti-coincidence detection system achieves enhanced energy resolution and superior background suppression, offering a promising solution for high-precision gamma-ray measurements in complex mixed-field environments.