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Abstract

Liquid argon (LAr) sampling calorimeters are employed by ATLAS for all electromagnetic calorimetry and for hadronic and forward calorimetry in the region 1.5 < |η| < 4.9. In the first LHC run a total luminosity of 27 fb−1 has been collected at center-of-mass energies of 7–8 TeV . After detector consolidation during a long shutdown, Run-2 started in 2015 and 139 fb−1 of data at a center-of-mass energy of 13 TeV have been recorded. In order to accomplish the Level-1 acceptance rate of 100 kHz in Run-2 data taking, the number of read-out samples recorded and used for the energy and the time measurement has been modified from five to four while keeping the expected performance. The well calibrated and highly granular LAr Calorimeter reached its design goals, both in terms of energy and direction measurement. This contribution gives an overview of the detector operation, hardware improvements, monitoring and data quality procedures, as well as the achieved performance, including the calibration and stability of the electromagnetic scale, noise level, response uniformity and time resolution.