Commissioning of the ATLAS Liquid Argon Calorimeter

The Liquid Argon (LAr) calorimeter is one of the main sub-detectors of the ATLAS experiment at the CERN LHC collider (Geneva, Switzerland). It provides precision measurements of electrons, photons, jets and missing transverse energy produced in the LHC pp collisions. The in situ commissioning of the LAr calorimeter has been ongoing since 2006. It has been extensively tested with frequent calibration runs, with cosmic ray muons, and with single proton beams circulating in the LHC ring. A selection of commissioning studies is presented. Their results show that the LAr calorimeter performs according to our expectations.