The EXTRA-BL4S experiment for the measurement of the energy and angular distributions of transition radiation X-rays

We have designed and implemented an experiment to measure the angular distributions and the energy spectra of the transition radiation X-rays emitted by fast electrons and positrons crossing different radiators. Our experiment was selected among the proposals of the 2021 Beamline for Schools contest, a competition for high-school students organized every year by CERN and DESY, and was performed at the DESY II Test Beam facility area TB21, using a high-purity beam of electrons or positrons with momenta in the range from 1 to 6 GeV/c. The measurements were performed using a 100 um thick silicon pixel detector, with a pitch of 55 um. Our results are consistent with the expectations from the theoretical models describing the production of transition radiation in multilayer regular radiators.