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 measurethe angular distributions and the energy spectra of the transitionradiation X-rays emitted by fast electrons and positrons crossingdifferent radiators. Our experiment was selected among the proposalsof the 2021 Beamline for Schools contest, a competition forhigh-school students organized every year by CERN, and was performedat the DESY II Test Beam facility area TB21, using a high-puritybeam of electrons or positrons with momenta in the range from 1 to6 GeV/c. The measurements were performed using a100 μm thick silicon pixel detector, with a pitch of55 μm. Our results are consistent with theexpectations from the theoretical models describing the productionof transition radiation in multilayer regular radiators.