The Phase-I Upgrade of the ATLAS Level-1 Calorimeter Trigger

The ATLAS Level-1 Calorimeter Trigger (L1Calo) is a hardware-based system that identifies events containing calorimeter-based physics objects, including electrons, photons, taus, jets, and missing transverse energy. L1Calo underwent a significant programme of upgrades for Run 3 of the LHC which is running at higher energies and instantaneous luminosity. The existing hardware will be replaced by a new system of FPGA-based feature extractor (FEX) modules, which processes finer-granularity information from the calorimeters and execute more sophisticated algorithms to identify physics objects; these upgrades will permit better performance in a challenging high-luminosity and high-pileup environment. The features of the upgraded L1Calo system will be introduced and the current status of installation and commissioning. In addition, the expected performance of L1Calo in Run 3 will be discussed.