Development of the radiator for the TRD of the ALICE experiment

The Transition Radiation Detector (TRD) of the ALICE experiment has the purpose to extend the capabilities to measure electrons of high transverse momenta[1]. By this the sensitivity to measure hard processes, in particular charm and beauty production is increased. In addition, the TRD will be used as a trigger detector on high pT-electrons. With this the measurement of jets with high transverse momenta will be possible. Transition radiation is produced, if a highly relativistic particle traverses the boundary between two media of different dielectric constants[2]. As the average energy of the emitted photon is related to the γ of the particle, this provides a means to discriminate electrons and pions. However, since the emission probability is small, a large number of boundaries have to be combined to obtain a reasonable efficiency. Commonly used are foil stacks of a few hundred polypropylene foils. However