Commissioning of the ATLAS Liquid Argon Calorimeter

The ATLAS liquid argon (LAr) calorimeter system consists of an electromagnetic barrel calorimeter and two end-caps with electromagnetic, hadronic and forward calorimeters. Since the installation of the LAr calorimeter in the ATLAS cavern, the electronic calibration of the readout system has been continuously exercised in the commissioning phase. The large amount of collected calibration data allows careful studies of the stability of constants, like pedestals and pulse shapes. The analysis of the large cosmic muon data samples and of the beam splash events that occurred on September 2008 has allowed to measure the in-situ calorimeter performance that was found to be close to the expectations.