Hydrogenated amorphous silicon (a-Si:H) p-i-n diodes applied to radiation detection

This work concerns the development of amorphous silicon (a-Si:H) based electromagnetic radiation detectors with the purpose of imaging applied to non-destructive testing and medical applications. The detector shown in this work was built with a-Si:H photodiodes coupled with thallium activated cesium iodide scintillators, CsI(Tl) and runs in current mode. The characterization of the detector was made by means of an 241 Am gamma radiation source whose main photon energy is 60 keV. The purpose of these tests was the evaluation of the detector behaviour in an energy range close to the one usually employed in medical applications. The intensity conditions of the source used allowed the detector to be evaluated at its lowest sensitivity threshold. The effects of reverse polarization in the dark current have been investigated. A prototype of a linear detector array was built for computed tomography systems use. The front-end (read-out) electronics was developed, assembled and tested. Tomographic images obtained with the a-Si:H based detectors are shown. The results obtained from the mathematical model of the detector have been compared to the experimental data. (author)