A Novel Optical Chamber Design and Shielding Optimization for Application in Liquid Scintillation Counting

Abstract Liquid Scintillation Counting (LSC) is a technique widely employed for measuring the activity of radioactive isotopes, finding applications in fields such as radioactive isotope measurements, nuclear material analysis, environmental monitoring, and nuclear medicine. This study is based on the Triple-to-Double Coincidence Ratio (TDCR) method within liquid scintillation counting, proposing a novel TDCR-LSC detector structure with a TriL-shaped optical chamber. Compared to traditional TDCR structures, the TriL-shaped optical chamber integrates the U-shaped design from the Pacific Northwest National Laboratory (PNNL) and the conventional TDCR structure. This is achieved by cutting three L-shaped hollow light guide tubes in the shielding, directing the light from the liquid scintillation vial at a 90° angle into three vertically positioned photomultiplier tubes (PMT). The design avoids the need for heavy external shielding around the PMT, and the L-shaped light guide prevents external radiation from directly entering the sample, thereby enhancing the shielding performance. The TriL-shaped design exhibits significantly improved shielding efficiency compared to the traditional TDCR structure. Validation through Geant4 simulations demonstrates that the TriL-shaped design outperforms the traditional TDCR structure in terms of shielding efficiency while maintaining efficient light collection. This research introduces a novel design approach to enhance the performance of liquid scintillation counting detectors.