Assessment of Gamma-Ray Spectrum Transmission with Scintillator Shading Variations for Determining Minimal Transmission Diameter

Gamma-ray spectroscopy is essential for identifying radioactive sources, but direct coupling of scintillators to photodetectors risks exposing sensitive electronics to radiation damage in high-radiation environments. Optical fibres offer a safer alternative by transmitting scintillation light over long distances, although differences in diameter can reduce spectral resolution for larger crystals, making precise spectroscopy difficult. To address this issue, we introduce an experimental setup that uses an adjustable iris and aperture plate to simulate fibre cores of various diameters, paired with scintillators of different sizes. We systematically measured the transmitted light intensity and spectral peak resolution at each aperture setting to analyse the relationship between core diameter, scintillator size, and spectral resolution. By optimising the balance between scintillator size and effective aperture, we can retain the advantages of larger crystals, enabling spectral analysis with smaller detection diameters. This work offers practical guidelines for selecting optimal configurations of detector and scintillator sizes, which are essential for monitoring gamma radiation with an optimal balance of high resolution and sufficient sensitivity.