ATLAS Pixel Detector operation and performance

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 M electronic channels, providing typically three measurement points with high resolution for particles emerging from the beam-interaction region, thus allowing to measure particle tracks and secondary vertices with very high precision. The completed Pixel Detector was operated for many months under realistic conditions in the ATLAS experimental hall, after installation. Calibration data has been taken and analyzed to determine the noise performance of the system. Combined operation with other subdetectors in ATLAS allowed to qualify the detector with physics data from cosmic muons. In this talk, a review of the commissioning and first operational experience of the Pixel Detector will be presented, including monitoring and calibration procedures, and the timing optimization process, as the detector operation progressed from commissioning with cosmic ray data to commissioning with collisions and finally to steady-state data taking. In addition, the Pixel Detector response to LHC high energy proton-proton collisions will be presented