Status of the ATLAS Pixel Detector at the LHC and its performance after three years of operation

he ATLAS Pixel Detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN, providing high-resolution measurements of charged particle tracks in the high radiation environment close to the collision region. The detector provides hermetic coverage with three cylindrical layers and three disks of forward and backward pixel detectors It consists of approximately SO million pixels that are individually read out via front-end chips bump-bonded to 1744 n-in-n silicon substrates. After three years of operation the detector performance is excellent: 96% of the pixels are operational at 3500 e threshold, with noise, occupancy and efficiency better than the design specifications. The effect of radiation on the silicon sensor is measured and matches expectations