The use of optical fibers as passageways for the scintillation light produced in CaF2 (Eu) powder in water for low-level tritiated water measurement

Abstract

A solid scintillation counting (SSC) system which uses the mixture of CaF2(Eu) powder and tritiated water inside the chamber room will be developed for the measurement of low-level tritiated water. However, the coincidence detection efficiency and net count rate might be limited by the photon absorption in the chamber of the SSC detector. This paper discusses the feasibility of using light guide fibers as the optical passageway in the chamber room by Geant4 simulation. The simulation results show that the performance of the detector can be improved by using wavelength-shifting fibers as optical passageway in the chamber. The detector can maintain a 4.2% coincidence detection efficiency at a 6 cm chamber thickness, and the detection limit can be as low as 0.47 Bq/mL under 10 min measurement. As a result, using wavelength-shifting fibers as optical passageways in the chamber room of the SSC system is possible and effective.