The ATLAS Trigger System: Ready for Run 2

The ATLAS trigger system has been used successfully for data collection in the 2009 -2013 Run 1 operation of the CERN Large Hadron Collider at centre-of-mass energies of up to 8 TeV. With the restart of the Large Hadron Collider for the new Run 2 data-taking period at 13 TeV, the trigger rates are expected to rise by approximately a factor of 5. Here we present a brief overview of the upgrades to the ATLAS trigger system that have been implemented during the shutdown period in order to deal with the increased trigger rates while efficiently selecting the physics processes of interest. These upgrades include changes to the Level-1 calorimeter trigger, the introduction of a new Level-1 topological trigger module, improvements in the Level-1 muon system, and the merging of the previously two-level High Level Trigger system into a single processing farm.