An Open-Source Monte Carlo Simulator for High-Z Semiconductor Detectors with a Charge Cloud Discretization Method

A Monte Carlo simulator is presented to evaluate the spectroscopic response of high-Z semiconductor pixel radiation detectors starting from the first principles of physical laws. It performs simulation in three different domains: electrostatic fields, photon-matter interaction, and photo-generated charge-carriers transport. A sampling algorithm is proposed to address the issue of fast and accurate computations of charge cloud dynamics in the presence of both diffusion and electrostatic repulsion effects, avoiding direct numerical integration of the induced current equation stated by the Shockley-Ramo theorem under a constant electric field hypothesis. The simulator is written as an object-oriented programming (OOP) source code repository, relying on the integration between MATLAB and COMSOL Multiphysics, and can be run with one executable script. The simulator architecture is presented, followed by a detailed explanation of all the physical models and implemented simulation strategies. The simulator is validated with experimental energy spectra acquired with a radiation detection system based on cadmium zinc telluride (CdZnTe) pixel detectors and ultralow-noise front-end electronics with state-of-the-art energy resolution.