Transition Radiation Spectroscopy with Prototypes of the ALICE TRD

Measurements of TR yield and spectra for a large variety of regular radiator configurations have been presented by different authors. In general, data confirm the theoretical predictions [1], although total TR yield and dependence on the momentum of the emitting particle are not always reproduced [2][3]. The ALICE Transition Radiation Detector (TRD) consists of 540 drift chambers with mixed fibre/foam radiators. The expected performance of the detector in heavyion collisions is investigated in detailed simulations of the detector response. An accurate numerical treatment of TR production in an irregular-layered radiator requires knowledge of the distributions of material thickness and spacing in the medium [4], information usually not easy to quantify with precision. A realistic implementation of the ALICE TRD radiator in the simulations requires measurements of the spectral distribution of the emitted TR.