The AMS silicon tracker: Construction and performance

Eight layers of double sided silicon microstrip sensors immersed in a 0.8 T magnetic field constitute the core of the AMS-02 apparatus. In each layer, simultaneous measurements of position and energy loss in silicon are performed along the particle trajectory. With its high spatial resolution, the silicon tracker will determine the rigidity (R) and the charge sign of particles up to several TVs, with a relative resolution 2.5% at R < 100 GV . The low noise and wide dynamic range of the silicon readout electronics allow to exploit the energy loss measurements to determine the particle absolute charge for nuclei up to Fe. The AMS tracker construction has been completed and it will be integrated into the AMS experiment during the 2007. The performances of the silicon detectors observed under various beam tests are presented focusing on the spatial resolution and on the charge separation capability.