Speaker
Description
The ALICE experiment underwent major upgrades during the LHC Long Shutdown 2 (2019–2022), including the installation of the new Inner Tracking System, ITS2. The detector consists of seven layers based on ALPIDE CMOS Monolithic Active Pixel Sensors, comprising 12.5 billion pixels over an active area of about 10 m² and providing an intrinsic spatial resolution of about 5 µm. With its high granularity, low material budget of 0.36% X₀ per layer in the innermost layers, and the first detection layer placed at a radius of 23 mm from the interaction point, ITS2 was designed to improve tracking efficiency and impact-parameter resolution, particularly at low transverse momentum.
ITS2 has been operated throughout LHC Run 3 across a range of collision systems, including proton–proton, Pb–Pb and short special runs with lighter ions. This contribution will present a Run 3 overview of detector operation, calibration strategy, data-quality monitoring and tracking performance. Particular attention will be given to long-term detector stability, operational procedures, beam background mitigation, and the experience gained in maintaining a large-area MAPS-based tracking detector under routine LHC running conditions. The presentation will also summarise the main Run 3 lessons, providing input for the future ALICE ITS3 upgrade and next-generation silicon tracking systems, including detector concepts for ALICE 3.