An Optimized Design of Single‐Channel Beta‐Gamma Coincidence Phoswich Detector by Geant4 Monte Carlo Simulations

An optimized single‐channel phoswich well detector design has been proposed and assessed in order to improve beta‐gamma coincidence measurement sensitivity of xenon radioisotopes. This newly designed phoswich well detector consists of a plastic beta counting cell (BC404) embedded in a CsI(Tl) crystal coupled to a photomultiplier tube. The BC404 is configured in a cylindrical pipe shape to minimise light collection deterioration. The CsI(Tl) crystal consists of a rectangular part and a semicylindrical scintillation part as a light reflector to increase light gathering. Compared with a PhosWatch detector, the final optimized detector geometry showed 15% improvement in the energy resolution of a ^131mXe 129.4 keV conversion electron peak. The predicted beta‐gamma coincidence efficiencies of xenon radioisotopes have also been improved accordingly.