First Results from GLAST-LAT Beam Test at CERN-PS and SPS

The GLAST Large Area Telescope (LAT) is a high-energy gamma-ray observatory sensitive to gamma rays in the energy range between 20 MeV and 300 GeV. The LAT consists of an array of tracking tower modules (TKR), composed of planes of silicon-strip detectors (SSDs) interleaved with converter tungsten layers, followed by a calorimeter (CAL) and surrounded by an anticoincidence system (ACD). The photon detection is based on the pair conversion process and silicon-strip detectors will reconstruct tracks of electrons and positrons. During the summer, a beam test campaign at CERN PS and SPS has been made in order to study the performance of a Calibration Unit (CU), consisting of two TKR modules and tree CAL modules. Experimental results on the performance of the tracker towers will be discussed