The ATLAS Liquid Argon Calorimeter: Construction, Integration, Commissioning

The ATLAS liquid argon (LAr) calorimeter system consists of an electromagnetic barrel calorimeter and two end-caps with electromagnetic, hadronic and forward calorimeters. The liquid argon sampling technique, with an accordion geometry, was chosen for the barrel electromagnetic calorimeter (EMB) and adapted to the end-cap (EMEQ geometry. The hadronic end-cap calorimeter (HEC) relies on a copper-liquid argon sampling technique with flat plate geometry and is divided in depth in two wheels per end-cap. Finally, the forward calorimeter (FCAL) is built with three modules made of cylindrical electrodes with thin argon gaps. The construction of the full calorimeter system is complete since mid-2004. The various modules built in the various home institutes of the collaboration were integrated into wheels at CERN in 2003-2004, and inserted in the three cryostats. Before the lowering in the ATLAS cavern, all the detector parts were tested at cold i.e. in cryostats filled with liquid argon at nominal temperature (87 degK). Results of these quality checks will be reported. End 2004, the EMB was installed in the ATLAS cavern and since then the front-end (FE) electronics has been installed on the detector and tested and is being connected to the back-end (BE) electronics sitting in a small cavern 70 meters away from the detector. The end-caps have been installed in the cavern in December, 2005 and April, 2006 and their electronics installation is ongoing. Since autumn 2006, a cosmic run based on the EMB together with some hadronic tile calorimeter modules is on going. Results of the first commissioning phase and preliminary results from the cosmic run will be presented to demonstrate the high standards of quality control met by our detectors.