Combined Medipix based imaging system with Si and CdTe sensor

Abstract

Medipix family detectors prove to be excellent tools for many different applications including the field of X-ray imaging. One of the main advantages of these devices is that the hybrid nature of the Medipix2 device allows using the same readout chip with different sensor materials (Si, GaAs, CdTe…). The idea presented in this work is to arrange the stack of two Medipix2 devices equipped with the Si (0.3 mm thick) and CdTe (1 mm thick) sensors to use the advantage of both materials for X-ray imaging during single exposure. Top Si layer is used to measure low energy X-rays benefiting from the excellent sensor material homogeneity. Bottom CdTe layer is used for measuring X-ray photons with higher energies taking the advantage of much higher detection efficiency of CdTe material in this part of incident spectra. By combining information from both sensitive layers it is possible to obtain high contrast, high spatial resolution images and also opens up the possibility to evaluate the sample material composition. This approach can be used with advantage in cases where both low and high contrast samples has to be imaged in the same time (soft tissue and bones, teeth, metal implants, composite materials, glued junctions, capacitors,…). Images of sample objects of this kind are presented in the paper.