Coupled Geant4-SPICE optimization of a portable CdTe-based alpha detector for environmental radon monitoring

Radon (²²²Rn) and its alpha-emitting progeny are major contributors to natural background radiation and a leading cause of lung cancer in non-smokers. This work presents the design and simulation of a portable alpha detector based on cadmium telluride (CdTe) technology for environmental radon monitoring. The system combines a compact, CAD-modeled housing with an optimized radon diffusion inlet and a low-noise CSA-CR-RC readout chain. Coupled Geant4 particle transport and SPICE electronics simulations were performed under realistic conditions (50-1000 Bq/m³, 0-40 °C, 20-90% RH). Results show a sensitivity of 0.15 cps/(Bq/m³), energy resolution better than 2% FWHM at 5.49 MeV, and < 15 min response for significant concentration changes. In contrast to previous CdTe-based alpha detection studies, which primarily focused on detector characterization under laboratory conditions, the present work introduces an instrument-level design framework that couples Geant4 particle transport, SPICE electronics modeling, and CAD-based housing optimization specifically for portable radon monitoring. This integrated approach enables simultaneous optimization of sensitivity, response time, and environmental robustness within a compact, battery-operated platform. The resulting design not only offers portability, robustness, and high-resolution alpha spectroscopy, but also establishes a transferable methodology for developing next-generation portable radon monitors for residential, occupational, and outdoor environments.