A novel theoretical model framework for the 3D CdZnTe drift strip detector

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Advances in data analysis and model prediction offer new potential for enhancing radiation measurement technologies, particularly in detector characterization and real-time signal analysis. A key challenge is creating realistic detector models that accurately describe the complex physical processes of photon-matter interaction, signal formation including material characteristics, and measurement to enhance design optimization and detector physics understanding. This research study introduces the development of an Advanced Theoretical Detector Model (ATDM) framework to evaluate the physical effects of charge diffusion, repulsion, and trapping, enabling the generation of realistic detector-specific signals through model prediction. Using physics simulations, the ATDM geometry, material properties, electric fields, and electrode weighting potentials are modeled for the DTU Space large-area (16 cm2) 3D CZT drift strip detectors. The simulations are based on the adjoint equations method, which when applied to the charge continuity equation allows deriving a description of underlying Charge Induction Efficiency (CIE) in the model. This allows for precise 3D mapping of induced charge at any time or interaction position. Additionally, Monte Carlo simulations generate recoiled photo-electron trajectories in CZT, which, combined with simulations of their propagation and secondary scattering processes yield a realistic charge cloud distribution. Model verification is achieved through experiments using narrow slit-beam illumination from a 137Cs source, measuring pulse shapes in the 40×40×5 mm3 detector modules with 69 readout channels. The ATDM framework, applicable to various detector types, successfully captures experimental data, offering insights into the pulse shape formation, timing, and intrinsic detector parameters that could guide future electrode configuration optimization and on the fly photon-by-photon measurements. The results also suggest a potential for electron tracking capability in 3D CZT drift strip electrodes, an exciting development that could significantly advance polarimetry and Compton imaging instruments for the future high-energy missions.