Transition radiation measurements with a Si and a GaAs pixel sensor on a Timepix3 chip

Growing energies of particles at modern or planned particle accelerator experiments as well as cosmic ray experiments require particle identification at gamma-factors (γ) of up to ∼10 5 . At present there are no detectors capable of identifying charged particles with reliable efficiency in this range of γ. New developments in high granular pixel detectors allow one to perform simultaneous measurements of the energies and the emission angles of generated transition radiation (TR) X-rays and use the maximum available information to identify particles. First results of studies of TR energy-angular distributions using gallium arsenide (GaAs) sensors bonded to Timepix3 chips are presented. The results are compared with those obtained using a silicon (Si) sensor of the same thickness of 500 μm. The analysis techniques used for these experiments are discussed.