A First Principles Method to Simulate the Spectral Response of CdZnTe-Based X- and Gamma-Ray Detectors

In this chapter we will present a recently developed simulation system using first principle calculations. The first block is based on Geant4 and is devoted to the simulation of the radiation-matter interaction. This toolkit allows to define the photon source type, any possible collimators or filters, the properties of sensing material and the geometrical configuration of the whole system. Simultaneously, the second block calculates the electric and weighting fields through a finite element method given the material properties, the geometry of the electrodes and the applied bias voltage. By combining the interaction positions of each photon and the deposited energy with the information provided by the second block, the charge transport and signal induction can be calculated by solving the equation of motion. In the last step, the spectrum can be reconstructed by applying the operations of the read-out electronics on the simulated current transients. We will present a comparison between simulated and real spectra in a wide range of radiation energies and for detectors with extremely different geometries and dimensions.