Status of the Atlas Liquid Argon Calorimeter and its Performance after two years of LHC operation

The ATLAS experiment is designed to study the proton-proton collisions produced at the Large Hadron Collider(LHC) at CERN. Liquid argon sampling calorimeters are used for all electromagnetic calorimetry covering the pseudo-rapidity region up to 3.2, as well as for hadronic calorimetry in the 1.5-3.1 region and the most forward part in the 3.1-4.9 region. The electromagnetic calorimeters use lead as passive material and are characterized by an accordion geometry that allows a fast and uniform azimuthal response without any gap. Copper were chosen as passive material for the hadronic section and copper and tungsten for the forward calorimeters; whereas a classic plate geometry was adopted at large polar angles, an innovative one based on cylindrical electrodes with thin argon gaps was designed for the forward coverage at low angles, where the particles flow is higher.