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 ∼ 105. 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 μ m. The analysis techniques used for these experiments are discussed.