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Ionizing radiation detection devices have been widely used in recent years in various applications and experimental fields, such as high energy physics, nuclear physics, and medical imaging. Detailed description of their operational properties and their characterization by means of numerical modelling, as simulations, are key issue to understand the characteristics of radiation detectors in terms of efficiency, resolution and signal-to-noise ratio, since they allow optimising parameters that will be further used. The modelling processes, as the simulations, are routinely carried out using various tools, like Monte Carlo approaches, for instance: PENELOPE, FLUKA or GEANT4 are used to study the interaction of the radiation with the detector accounting for the whole physical processes. However, transporting electron/hole pairs, as generated through the device sensor to conform the corresponding electronic signals uses tools based on the finite element method, such as TCAD (Technology Computer Aided Design), which are developed mainly to help the microelectronics industry to design products. Usually, modelling approaches for radiation transport and electonic signal production are not integrated, thus performing the simulation process by splitting the problem intosucessive independent phases. Within this framework, the present study proposes, implements, and reports on a novel methodology that allows combining the two approaches aimed at integrating the complete simulation, thus achieving a step-by-step integrated modelling flow to describe the interaction of ionizing radiation with the sensor along with the transport of the generated charge to the photodiodes and, finally, to the generation of electronic signals.

In recent years, the study of X-ray spectrometry has promoted significant advances in various scientific areas, thus increasing the implementation of ionizing radiation in many applications of modern technology. Typical X-ray spectrometry systems consist of a set of devices that allow this radiation to be converted into a detectable electrical signal. The main spectrometer components include: the sensitive volume (detector), the multichannel pulse processing device, and the associated software. Cadmium telluride (CdTe) has been introduced as a suitable bulk-sensing semiconductor material that reports higher efficiency compared to silicon diodes. Then, the Amptek XR-100T-CdTe spectrometer, has gained wide applications during the last years, mainly due to its performance achieving high efficiency up to 100 keV.The present work reports on the characterization of detector response for the Amptek XR using Monte Carlo simulations, while separately accounting for the contribution of the different spectrometer components. To this aim, the geometry along with the elemental composition properties of the different components have been carefully included in the simulation setup. A kernel based approach has been implemented to study the response of the detector using narrow monoenergetic X-ray beams having incident kinetic energy within [5-1000] keV, and discriminating the relative contribution for each kernel attributable to the different spectrometer components. Finally, the simulation results have been compared with the efficiency curve reported by the manufacturer, showing good agreement with the kernel based approach characterization when the CdTe sensitive volume along with the Be vacuum window are taken into account.