Simulation study based on the development of lanthanum bromide-cesium iodide anti-Compton γ detector spectrometer

The simulations systematically varied detector dimensions and configurations to compare the two scintillator materials. Based on these simulation results, the optimized parameters for standalone LaBr3:Ce and CsI:Tl detectors were determined. Subsequently, the performance of an anti‑Compton gamma‑ray spectrometer, composed of a central LaBr3:Ce detector surrounded by multiple CsI:Tl detectors, was simulated in Geant4.

For the integrated spectrometer, the energy deposition and coincidence events between the central and surrounding detectors were analyzed to evaluate the Compton suppression capability. [Results]: The simulations of standalone detectors with a 137Cs standard source yield the following optimized geometries: a cylindrical LaBr3:Ce detector (2 inches in diameter and length) and a regular hexagonal prismatic CsI:Tl detector (55 mm across flats and 200 mm in length).

The integrated LaBr3:Ce–CsI:Tl anti‑Compton gamma‑ray spectrometer, comprising one LaBr3:Ce detector and six CsI:Tl detectors, is tested in simulation using a 137Cs source. The results give a Compton suppression factor (CSF) of 5.13, and the Compton‑to‑peak ratio improves from 14.69 (without suppression) to 75.36 (with suppression). [Conclusions]: The LaBr3:Ce–CsI:Tl anti‑Compton gamma‑ray spectrometer developed in this study effectively suppresses Compton scattering events, leading to a substantial enhancement in spectral quality.

Such a detection system can therefore provide reliable experimental data to support the treatment of radioactive offgas generated by thorium‑based molten salt reactors.