New test beam results with prototypes of the ALICE TRD

We present measurements of ionization energy deposit in Xe , CO 2 (15%) and of transition radiation in an irregular radiator. The measurements are performed with prototypes of the ALICE Transition Radiation Detector (TRD) with a beam of electrons and pions of 1– 10 GeV / c . We also present resulting electron–pion separation performances for the prototype chambers as well as for final, full-size TRD chambers.