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

The Schottky barrier line-scanning X- and γ-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 241Am 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)×0.25 mm2 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 (∼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.