CadTool: An End-to-End Semiconductor Detector Simulation Tool

CdTe and CdZnTe (CZT) sensors have attracted significant attention over the past 25 years as room-temperature semiconductor detectors for hard X-ray and γ-ray detection, with applications in astrophysics, medical imaging, non-destructive testing, and nuclear security. Their appeal lies in the combination of compact form factor, high stopping power, wide bandgap and favourable charge-transport properties. We present CadTool, an end-to-end simulation tool that combines GATE 10/Geant4 for photon transport and energy deposition with the SolidStateDetectors.jl library for electric-field calculation, charge transport and signal induction, followed by a modular electronics-readout model that produces digitized data in the same format as the corresponding experimental detector. We compare simulations with measurements from three CdTe detector configurations, simulated with a single set of charge-transport parameters: a 1 mm thick pixel detector and 1–2 mm thick double-sided strip detectors, all with a 250 µm pitch, under 241Am illumination, and a 2 mm thick pixel detector with an 800 µm pitch irradiated with 133Ba and 137Cs up to 662 keV. For the pixel detector and the 1 mm strip detector, the measured and simulated energy spectra below 70 keV differ by 7–12 % of their events, and the dominant one- and two-electrode multiplicity classes agree within 20%. At 662 keV, the inter-pixel charge loss agrees within their respective uncertainties, the mean cluster size within 1.2% and the multiplicity fractions within 1.73%. CadTool is intended to support the design and optimisation of future detector and Application Specific Integrated Circuit (ASIC) systems, provide detailed detector-response models for larger-scale simulations, generate synthetic datasets, and improve the understanding of charge-transport and signal-formation processes in semiconductor detectors.