Performance Characterization of Amorphous Silicon Digital Detector Arrays for Gamma Radiography

This paper reports the performance characteristics of a-Si detectors with Ir-192 gamma source. Imaging performance of the detector system is evaluated using contrast sensitivity over a range of material thickness of steel, signal to noise ratio, dynamic range and linearity. The radiographic sensitivity was observed over a range of thickness of steel using standard image quality indicators. Quantum efficiency of the scintillator material (CsI) for Ir-192 and Co-60 was studied using theoretical models. For Ir-192 source both theoretical models and experiments were performed to find the minimum and maximum thickness limitation for steel using the a-Si detector system. Various configurations of pipe weld with defects such as lack of fusion, penetration, tungsten inclusion and porosities were studied to evaluate the imaging performance.