Experimental verification of a dual-Gaussian charge diffusion model for pixel sensors with heavy ions

The Monolithic Active Pixel Sensor (MAPS), known for its excellent position resolution, has been widely applied in fields such as particle physics, nuclear physics, and radiation imaging. In Monte Carlo simulations, the lack of an analytical model for charge collection and diffusion at the pixel sensor level can often lead to significant deviations between simulation and experimental results. This study proposes a dual-Gaussian charge-diffusion model for pixel sensors to describe the charge-diffusion process of heavy-ion particles within a specific range in MAPS pixel sensors. Using the Topmetal − M sensor as a prototype, the dual-Gaussian charge diffusion model was used to simulate the charge diffusion and collection processes of particles 18 40 A r and 73 181 T a on the sensor via Geant4. The simulation results were compared with the experimental data, producing the necessary fixed parameters for the model ( σ 1 =0.04, σ 2 =0.143, ω =0.926), resulting in high consistency between the model and the experimental data in terms of particle cluster size and charge distribution. This set of parameters was further applied to predict the clustering behavior of the particles 6 12 C , with mean deviations from the experimental results of less than 0.23%. This study provides a theoretical model for the charge diffusion behavior of heavy particles in MAPS, laying the foundation for improved efficiency and accuracy in pixel sensor simulations within Monte Carlo frameworks. The findings have significant implications for the application of pixel sensors in nuclear physics, particle physics, and radiological imaging.