Speaker
Description
Determining detector efficiency in $\gamma$ spectroscopy often relies on expensive and time-consuming experimental calibrations. This study presents a validated Monte Carlo simulation approach as a flexible and cost-effective alternative. Using RayXpert$^{®}$, we modeled the complex interactions of $\gamma$ photons with HPGe and NaI(Tl) detectors, accounting for intrinsic detector properties such as dead layer thickness and Gaussian energy broadening. For HPGe detectors, the deviation between simulated and experimental efficiency curves was maintained below 5%. A case study involving a bread roll sample spiked with $^{134}$Cs and $^{137}$Cs, scanned using photogrammetry, demonstrated the method’s applicability to irregular geometries. However, unaccounted True Coincidence Summing (TCS) effects introduced biases for cascade-emitting isotopes. For NaI(Tl) detectors, simulations incorporated user-defined spectra to address the poorer energy resolution, yielding results within $\pm$10% accuracy, suitable for routine quality control or environmental monitoring. The simulations were complemented by high-resolution CT scans of the detectors to identify discrepancies between real and simulated geometries.
This work underscores the potential of Monte Carlo simulations to reduce calibration costs and improve accessibility for laboratories, while highlighting key limitations, such as TCS and geometric mismatches, that warrant further investigation.