The Phase-2 ATLAS ITk pixel upgrade

The new ATLAS ITk pixel system will be installed during the LHC Phase-2 shutdown, to better take advantage of the increased luminosity of the HL-LHC. The detector will consists of five layers of stave-like support structures in the most central region and ring-shaped supports in the endcap regions, covering out to |η| < 4. While the outer three layers of the Pixel Detector are designed to operate for the full HL-LHC data taking period, the innermost two layers of the detector will be replaced around half of the lifetime. The ITk pixel detector will be instrumented with new sensors and readout electronics to provide improved tracking performance and radiation hardness compared to the current detector. Sensors will be read out by new ASICs based on the chip developed by the RD53 Collaboration. The design and recent results of 3D and planar sensor technologies will be discussed, together with the module concept to be implemented in the ITk pixel system. A description of the pixel off-detector readout electronics, implemented in the framework of the general ATLAS trigger and DAQ system, will also be given. Results of extensive tests which are being carried out to prove the feasibility of implementing serial powering, the baseline for the ITk pixel system and multi-module readout will be presented.