FTK: An Hardware based Tracker for the ATLAS Experiment

During the Run-2 of the Large Hadron Collider (LHC) the instantaneous luminosityexceeds the nominal value of 10 34 cm −2 s −1 with a 25 ns bunch crossing periodand the number of overlapping proton-proton interactions per bunch crossingincreases up to about 80. These conditions pose a challenge to the triggersystem of the experiments that has to control rates while keeping a goodefficiency for interesting physics events. In order to facilitate the use oftracks in the High Level Trigger, the ATLAS experiment planned the installationof a hardware processor dedicated to tracking: the Fast Tracker (FTK). It isdesigned to deliver full-scan tracks with p T above 1 GeV to the ATLAS HighLevel Trigger system for every Level-1 (L1) accept. The Fast Tracker system willbe massive, with about 8000 Associative Memory chips and 2000 field programmablegate arrays, providing full tracking with a rate up to 100 kHz and an averagelatency below 100 microseconds. This document provides an overview of the FTKsystem, as well as reports on the commissioning status.