Results from prototype tests for the ALICE TRD

Electron ID and tracking in ALICE, in particular at the trigger level, require excellent TRD performance in terms of pion rejection and position resolution. We present results of prototype measurements in beams of 1–6 GeV/c. A position resolution down to 200 μm, angular resolution of 1° and pion rejection factors better than 100 are reached. Measurements of the ionization energy deposit and pure transition radiation spectrum are discussed.