Application of monolithic strip line radiation detector based on semi-insulating GaAs in X-ray portable scanner

The Schottky barrier line-scanning X- and gamma-ray detector is presented, based on bulk undoped semi-insulating (SI) GaAs suitable for radiography imaging with a high position resolution (the lowest pitch 0.125 mm). Basic electrical and detection characteristics of the detector (I-V dependences, pulse height spectra of Am-241 gamma source) together with evaluated parameters are demonstrated. The detector is irradiated from the edge with an estimated active area of the strip input cross-section (0.125-0.25) x 0.25 mm(2) and absorption length 1.25 or 2.5 mm. A photon-counting readout electronics with 480 channels has been developed, giving a total length of the scanner line of about 12 cm, using detectors with pitch 0.25 mm. The readout system is based on a 16 channel VLSI chip or on 24 channel modules produced with discrete components in SMD technology. Overall detection efficiency of the developed strip SI GaAs radiation detector reaches a value higher than 50% of the theoretical one (similar to 75%) for detection of 60 keV photons. The status of the development of a modular portable X-ray scanner based on the developed detectors is also presented. (C) 2004 Elsevier B.V. All rights reserved.