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

The ATLAS Pixel Detector is the innermost detector of the ATLAS experiment at the Large Hadron Collider at CERN. The detector provides hermetic coverage with three cylindrical layers and two endcaps with three disk layers each. It consists of 1744 n$^+$-in-n silicon modules with a total of about 80 million pixels that are individually read out via chips bump-bonded to the silicon substrate. In this note, results from the successful operation of the Pixel Detector during Run~1 of the LHC and its status after three years of operation will be presented. The record breaking instantaneous luminosities of up to $7.7 \cdot 10^{33}$ cm$^{-2}$ s$^{-1}$ recently surpassed at the Large Hadron Collider generate a rapidly increasing particle fluence in the ATLAS Pixel Detector. As the radiation dose accumulates, effects of radiation damage are now clearly observable in the silicon sensors: an increase in leakage current and change of the depletion voltage. Type inversion has been observed for the innermost layers. During the Long Shutdown 2013-2014, a fourth pixel layer will be added at the radius of 33~mm to address inefficiencies due to radiation damage and improve the performance beyond the current 3 layer pixel system. In addition, a replacement of pixel services will partially recover lost efficiency.