Estimate of large CZT detector absolute efficiency

This work presents a simulation study about the absolute spectroscopic performances of two large CZT coplanar detectors 1.5×1.5 cm² area, 1.0 cm thick. A code based on the Geant libraries and classical Monte-Carlo sampling has been developed for the simulation of the experimental scenarios. This tool adapts the Geant capabilities for simulating complex detection systems to the particular needs in spectroscopic studies. Initially, detectors with perfect charge transportation and collection have been simulated. Prior to the application to the CZT devices under research, the code is checked in the simulation of a reliable HPGe detector. The result for this detector is considered as reference for estimating the code capabilities. Some preliminary considerations are exposed in order to correctly define the true sensitive volume of the CZT detectors. Results from the simulation of this basic detector model are presented and commented. Subsequently, the effects of a possible realistic electric field profile in the coplanar detector unable to efficiently deflect the produced negative charge to the collecting anode is studied. From the analysis of the differences found between the simulated and real results, some conclusions relating the electrode design and detector quality are proposed