Commissioning and operation of the ATLAS pixel detector

The ATLAS Pixel Detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN. It consists of 1744 silicon sensors equipped with approximately 80 million electronic channels, providing typically three measurement points with high resolution for charged particles emerging from the beam-interaction region, thus allowing the reconstruction of particle tracks and secondary vertices with very high precision. Before the start of LHC operations, the completed Pixel Detector was operated for many months under nominal conditions in the ATLAS experimental hall. This allowed for the optimization of the operating parameters of the system, and to qualify the detector with physics data from cosmic muons. After the commissioning phase was complete, the Pixel Detector was 97.5% operational during the first LHC pp collisions run. Noise occupancy and hit efficiency exceed the design specifications. The alignment is close enough to the ideal to allow good track reconstruction and invariant mass determination. A review of the commissioning and first operational experience with the Pixel Detector will be presented. This will include detector calibration procedures, online data quality monitoring, module timing optimization and the status of the Pixel Detector during the first year of LHC operations. (C) 2010 Elsevier B.V. All rights reserved.