GLAST LAT silicon tracker

The Large Area Telescope (LAT) on the Gamma-ray Large-Area Space Telescope (GLAST) mission is designed to provide unprecedented sensitivity in the exploration of the gamma-ray sky. Gamma rays with energy above 10 MeV are detected via the pair conversion process, using a precision silicon tracker-converter and a hodoscopic CsI calorimeter. Charged cosmic rays are rejected by a tiled plastic-scintillator anti-coincidence detector. We report here on the design, prototyping, testing and expected performance of the silicon tracker-converter, which will be the largest silicon detector system in space after the GLAST launch in 2006. Specifically, we discuss the electronics system, the mechanical system, results from beam tests and a balloon flight, assembly procedures and prototyping experience, and expected performance of the tracker-converter.