A silicon microstrip tracker in space: Experience with the AMS silicon tracker on STS-91

The Alpha Magnetic Spectrometer (AMS) is designed as an independent module for installation on the International Space Station (ISS) in the year 2003 for an operational period of three years. The principal scientific objectiv es include the searches for antimatter and dark matter in cosmic rags. The AMS tracker uses silicon microstrip sensors to reconstruct charged-particle trajectories. A first version of the AMS, equipped with 2.1 m(2) of silico n sensors and a permanent magnet, was flown on the NASA space shuttle Disco very during June 2-12, 1998. In this contribution, we describe the detector and present results of the tracker performance during the flight.