ATLAS FTK: Fast track trigger

A track reconstruction system for the trigger of the ATLAS detector at the Large Hadron Collider is described. The Fast Tracker is a highly parallel hardware system designed to operate at the Level-1 trigger output rate. It will provide high-quality tracks reconstructed over the entire inner detector by the start of processing in the Level-2 trigger. The system is based on associative memories for pattern recognition and fast FPGA’s for track reconstruction. Its design and expected performance under instantaneous luminosities up to 3 10 34 =cm 2 =s are discussed.