Speaker
Description
Strontium-90 (Sr-90) contamination of groundwater at nuclear sites like Sellafield (UK) and both the Savannah River Site and Hanford (US) remains an environmental challenge. Sr-90's high mobility and solubility demand monitoring systems capable of real-time, in-situ measurement.
Recent work towards a portable, aquatic beta spectrometer has shown that ZnSe(Al,O) is a strong scintillator candidate for detecting and, characterising Sr-90. The current prototype couples a 42 mm diameter, 2.1 mm thick ZnSe(Al,O) crystal to a single SiPM. It was able to achieve 61.5% efficiency when benchmarked against an idealised optical simulation. Improving this efficiency and improving energy resolution requires transitioning to a multi-SiPM configuration. To address this, a Geant4-based optical model has been developed to evaluate SiPM number, spatial arrangement, and the choice of surface coating needed to minimise photon loss. Simulation results show diminishing returns beyond an 8 x 8 SiPM array, enabling optimisation of performance relative to system cost. Applying a coating to crystal improved collection efficiency by at least 35% compared to un-coated. Further simulations and experimental validation are to follow shortly. This optimisation stage is a critical step toward producing a fully field-deployable, high-efficiency Sr-90 spectrometer for groundwater monitoring.
Key Words: ZnSe(Al,O) scintillator detectors, environmental monitoring, real-time radiation instrumentation, silicon photomultiplier arrays, optical transport modelling.
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