Applications of pixellated GaAs X-ray detectors in a synchrotron radiationbeam

Hybrid semiconductor pixel detectors are being investigated as imaging devi ces for radiography and synchrotron radiation beam applications. Based on p revious work in the CERN RD19 and the UK IMPACT collaborations, a photon co unting GaAs pixel detector (PCD) has been used in an X-ray powder diffracti on experiment. The device consists of a 200 mum thick SI-LEC GaAs detector patterned in a 64 x 64 array of 170 mum pitch square pixels, bump-bonded to readout electronics operating in single photon counting mode. Intensity pe aks in the powder diffraction pattern of KNbO3 have been resolved and compa red with results using the standard scintillator, and a PCD predecessor (th e Ohm3). The PCD shows improved speed, dynamic range, 2-D information and c omparable spatial resolution to the standard scintillator based systems. It also overcomes the severe dead time limitations of the Ohm3 by using a shu tter based acquisition mode. A brief demonstration of the possibilities of the system for dental radiography and image processing are given, showing a marked reduction in patient dose and dead time compared with film. (C) 200 1 Elsevier Science B.V. All rights reserved.