First-year experience with the BaBar silicon vertex tracker

Within its first year of operation, the BaBar Silicon Vertex Tracker (SVT) has accomplished its primary design goal, measuring the z vertex coordinate with sufficient accuracy as to allow the measurement of the time-dependent CP asymmetry in the neutral B-meson system. The SVT consists of five layers of double-sided. AC-coupled silicon-strip detectors of 300 mum thickness with a readout strip pitch of 50-210 mum and a stereo angle of 90 degrees between the strips on the two sides. Detector alignment and performance with respect to spatial resolution and efficiency in the reconstruction of single hits are discussed. In the day-to-day operation of the SVT., radiation damage and protection issues were of primary concern. The SVT is equipped with a dedicated system (SVTRAD) for radiation monitoring and protection, using reverse-biased photodiodes. The evolution of the SVTRAD thresholds on the tolerated radiation level is described. Results on the first-year radiation exposure as measured with the SVTRAD system and on the so far accumulated damage are presented. The implications of test-irradiation results and possible future PEP-II luminosity upgrades on the radiation limited lifetime of the SVT are discussed