Characterization of GaAs:Cr Timepix hybrid pixel detectors
High resistivity gallium arsenide compensated by chromium fabricated by Tomsk State University has demonstrated a good suitability as sensor material for hybrid pixel detectors used in X-ray imaging systems with photon energies up to 60 keV. The material is available with thickness up to 1 mm and thanks to its Z number and fully active volume of the sensor high absorption efficiency in this energy region is provided.
In this work we report the recent results of characterization of the Timepix detectors hybridized with GaAs:Cr sensors of various thickness using synchrotron radiation and gamma sources. The energy and spatial resolution, mu-tau distribution over sensor area have been determined. By means of scanning the detector with pencil photon beam generated by synchrotron facility the geometrical mapping of pixel sensitivity is obtained as well as the energy resolution of a single pixel. The long-term stability of the detector has been evaluated based on the measurements performed over one year. Also the radiation hardness of GaAs:Cr sensors was investigated by means of irradiation with 20 MeV electrons and the results will be presented in comparison with Si sensors.