The ATLAS ITk Strip Detector System for the Phase-II LHC Upgrade

The ATLAS experiment at the Large Hadron Collider is currently preparing for a major upgrade of the Inner Tracking for the Phase-II LHC operation (known as HL-LHC), scheduled to start in 2026. In order to achieve the integrated luminosity of 4000 fb −1 , the instantaneous luminosity is expected to reach unprecedented values, resulting in about 200 proton-proton interactions in a typical bunch crossing. The radiation damage at the full integrated luminosity implies integrated hadron fluencies over 2×10 16 n eq /cm 2 requiring a completed replacement of the existing Inner Detector. Anall-siliconInnerTracker(ITk)isunderdevelopmentwithapixeldetectorsurrounded by a strip detector, aiming to provide increased tracking coverage up to | η |=4. The current prototyping, targeting an ITk Strip Detector system consisting of four barrel layers in the centre and forward regions composed of six disks at each end, is described in the ATLAS Inner Tracker Strip Detector Technical Design Report (TDR). With the recent final approval of the ITk strip TDR by the CERN Research Board, the prototyping phase is coming to an end and the pre-productionreadiness phase has started at the institutes involved. In this contribution an overview of the ITk strip detecot components is given, including measure- mentsofpartsirradiatedwitharangeoffluencesreachinguptotheHL-LHCdoses, demonstrating the excellent radiation hardness achieved.