The Pixel Detector of the ATLAS Experiment for the Run 2 at the Large Hadron Collider

The Pixel Detector of the ATLAS experiment has shown excellent performance during the whole Run 1 of LHC. Taking advantage of the long shutdown, the detector was extracted from the experiment and brought to surface, to equip it with new service quarter panels, to repair modules and to ease installation of the Insertable B-Layer (IBL). The IBL is a fourth layer of pixel detectors, and has been installed in May 2014 between the existing Pixel Detector and a new smaller radius beam-pipe. To cope with the high radiation and pixel occupancy due to the proximity to the interaction point, a new read-out chip and two different silicon sensor technologies (planar and 3D) have been developed. Furthermore, the physics performance will be improved through the reduction of pixel size while, targeting for a low material budget, a new mechanical support using lightweight staves and a CO$_2$ based cooling system have been adopted. The IBL construction and installation in the ATLAS Experiment has been completed very successfully. The IBL qualification has shown outstanding detector performance with less then 0.09% of bad pixels. The final commissioning is now on-going and the ATLAS Pixel Detector is ready to join the LHC Run 2 with an improved configuration and a new pixel layer.