The AMS TRD. A gasdetector designed for operation in space

The Alpha Magnetic Spectrometer AMS02 will be equipped with a large transition radiation detector TRD to achieve a proton background suppression necessary for dark matter searches. The AMS02 TRD consists of 20 layers of fleece radiator each with Xe/CO2 proportional wire straw tubes read out by a dedicated low-power data-acquisition system. A space qualified TRD design and production process will be presented. The detector performance and its GEANT simulation is verified with a 20 layer prototype tested at CERN with electrons, muons and pions up to 100 GeV and protons up to 250 GeV. The detector is under construction at RWTH Aachen, the gas system is built at MIT, slow-control at MIT and INFN Rome and DAQ at TH Karlsruhe. This project is funded by the German Space Agency DLR, the US Department of Energy DOE and NASA.