Applications of pixellated GaAs X-ray detectors in a synchrotron radiation beam

Hybrid semiconductor pixel detectors are being investigated as imaging devices for radiography and synchrotron radiation beam applications. Based on previous work in the CERN RD19 and the UK IMPACT collaborations, a photon counting GaAs pixel detector (PCD) has been used in an X-ray powder diffraction experiment. The device consists of a 200 mm thick SI-LEC GaAs detector patterned in a 64 64 array of 170 mm pitch square pixels, bumpbonded to readout electronics operating in single photon counting mode. Intensity peaks in the powder diffraction pattern of KNbO3 have been resolved and compared with results using the standard scintillator, and a PCD predecessor (the O3). The PCD shows improved speed, dynamic range, 2-D information and comparable spatial resolution to the standard scintillator based systems. It also overcomes the severe dead time limitations of the O3 by using a shutter 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. # 2001 Elsevier Science B.V. All rights reserved.