(A) study on the effectiveness of a light guide in a $\phi$2×2 inch NaI(Tl) scintillation detector coupled with a silicon photomultiplier

Abstract

This thesis study is about the effectiveness of a light guide in a silicon photomultiplier (SiPM)-based $\phi$2×2 inch thallium-doped sodium iodide (NaI(Tl)) scintillation detector for an unmanned radiation monitoring system. Previous studies have designed the SiPM-based detector using a light guide. The light guide has a positive effect of reducing the deviation of photon collection efficiency in the scintillator, but it reduces the pulse height due to the photon loss. Therefore, the light guide should be used when there is an obviously positive impact through accurate analysis. The optical simulation resulted that the light guide decreased in the deviation of photon collection efficiency, but significantly increased the statistical uncertainty. On the other hand, a SiPM (12×12 $mm^2$)-based detector with a10 mm or 30 mm light guide and a direct coupling system was tested. The direct coupling system showed better linearity within about 5% error. In addition, it achieved the best energy resolution at all energy peaks (especially, 9.76% at 662 keV).