The ATLAS Strip Detector System for the High-Luminosity LHC

The ATLAS experiment at the Large Hadron Collider is currently preparing for a significant upgrade of the Inner Tracker for the High-Luminosity LHC operation, scheduled to start in 2027. A planned integrated luminosity of 4000 $ \mathrm{fb^{-1}}$ implies integrated hadron fluences over $2\cdot10^{16}$ $\mathrm{n_{eq}/cm^2}$, requiring a complete replacement of the existing Inner Detector. An all-silicon Inner Tracker (ITk) is under development with a pixel detector surrounded by a strip detector. The Strip detector will consist of four barrel layers in the centre and forward regions composed of six disks at each end, with silicon-strip modules as basic units. With the production of modules scheduled to begin in 2020, a thorough understanding of the current prototype modules is critical. Electrical characterization of the module aims to asses the front-end performance in terms of input noise and noise occupancy. Input noise results from R0 modules built with different front-end designs are presented. Tracking resolutions and detection efficiency are evaluated in test beams. Several module prototypes have been built and tested in 2018 and 2019. In this report, the test beam results from a Long Strip and an R0 module are presented. Similarly, results from the first double-sided R0 prototype module, built using a carbon-fibre core with integrated services is shown. The results focus on hit detection efficiencies and spatial resolution of the modules. The electrical performance of prototypes with the production front-end design is also discussed