Development of A Multi-Layer Silicon Betaray Spectrometer for CANDU Environment and Preliminary Characterization

To echo the growing demand of precise assessment dose to lens of eye from beta radiation at Canada Deuterium Uranium (CANDU) power planet, we present a silicon-based beta-ray spectrometer that is able to measure the in situ beta-ray fluence spectrum and real-time dose monitor with a high gamma rejection ratio avoiding overestimation of beta dose in the beta-gamma mix environment at CANDU sites. A prototype has been developed that features one 500 $\mu \mathrm{m}$ and three $1500 \mu \mathrm{m}$ silicon detectors in series to measure a beta energy range of 70 keV to 3000 keV using the $\Delta \mathrm{E}$ vs. E method, which enables temporal coincidence and energy logic for electron channel binning. GEANT4 simulation was extensively conducted for the geometric factors and instrument response functions to facilitate the instrument design and characterization. The silicon beta spectrometer prototype was characterized under a beta-gamma mixed field consisting of ${ }^{90} \mathrm{Sr}$ and ${ }^{137} \mathrm{Cs}$ sources to evaluate the beta/gamma discrimination ability. In this paper, we report the project motivation, hardware description, GEANT4 modeling and preliminary characterization of the prototype system.