Performance of the AMS-02 silicon tracker in the ISS mission

The Alpha Magnetic Spectrometer (AMS-02) is a large acceptance cosmic-ray detector which has been installed as an independent module on the International Space Station (ISS) in May/2011 after the successful launch of STS-134. The instrument will provide a precise measurement of the cosmic-ray energy spectra and extensive antimatter search up to 1 ∼ 2 TeV for particle charges up to Z=26. The silicon tracker is working as expected as well as the other detector component. The temperature is controlled within a few degrees range by The Tracker Thermal Control System (TTCS) and the measured pedestal and noise level is stable in time. The intrinsic efficiency estimated with proton and helium data is greater than 95% for most of the ladders. In this paper the status and the performance of the tracker after the first several month of data taking in space is presented.