The Atlas liquid argon calorimeter at the CERN Large Hadron Collider: General performance and latest developments of the High Voltage system

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 the identification and characteristics measurement of the electrons, photons and hadronic jets. Since the first collisions in 2010, the calorimeters operated almost optimally, playing a leading role in the discovery of the Higgs boson announced in July 2012. A special emphasis in this paper will be given on the latest developments of the high voltage power supply system. These efforts allowed to equip the calorimeters with innovative power supply modules able to temporarily sustain high current load without major voltage drop.