Design of a Portable Phoswich Detector for Simultaneous α, β, and γ Identification

Abstract

During operation, nuclear facilities produce radioactive materials, solutions, or aerosols that form α/β/γ mixed radiation in the surrounding environment. Considering their differences in interaction mechanisms, hazards, and protection approaches, it is crucial to discriminate the radiation during measurement. Currently, for portable radiation monitors with simultaneous α/β/γ identification ability, there are two problems: small detection area and high misidentification ratio; in particular, some of them are too difficult in technique and extra expensive. Making use of range differences of α/β/γ, energy difference of α/β/γ in the mixed radiation and different luminescence properties of different scintillators, this study proposes a new large-area Phoswich (phosphor sandwich) design that can identify α, β and γ simultaneously and its corresponding pulse shape discrimination method with better accuracy using the combined information of position, amplitude and time. It is worth mentioning that a special identification circuit scheme with only threshold discriminators, coincidence logic, and counter is suggested to avoid complete waveform collection and analysis, which can increase the detector’s rate capability and identification accuracy. The detector was modeled in Geant4, and the analysis shows its good performance: the misidentification rates for α ( ²⁴¹ Am), β ( ⁹⁰ Sr- ⁹⁰ Y), γ( ¹³⁷ Cs) and γ ( ⁴⁰ K) are 0.00%, 0.33%, 7.28%, and 8.00%, respectively. This study will help improve the Phoswich detector’s performance in α/β/γ radiation measurement.