Speaker
Description
During the LHC Long Shutdown 3 (2026–2030), the ALICE collaboration will upgrade its three innermost tracking layers with the Inner Tracking System 3 (ITS3), the first fully cylindrical, wafer-scale silicon vertex detector. Built on 65 nm CMOS MAPS technology, ITS3 features silicon thinned to 50 µm and bent into self-supporting cylindrical layers at radii of 19, 25, and 32 mm. Wafer-scale stitching enables 27 cm-long seamless sensors with direct signal and power routing, eliminating flexible printed circuits over the active area and drastically reducing passive mass.
These self-supporting sensors maintain over 99% detection efficiency and a spatial resolution of approximately 5 µm. By combining this sensor technology with ultra-light carbon-foam support structures with forced-air cooling instead of traditional frames and water cooling, the total material budget drops to under 0.09% X0 per layer.
Extensive lab and test-beam campaigns have validated the ITS3 architecture, demonstrating stitching feasibility, high yield, and radiation hardness in earlier sensor prototypes. Currently, a characterisation campaign is underway for the final full-scale prototype, MOSAIX. Furthermore, full-scale engineering models have confirmed thermal and mechanical performance, showing that an 8 m/s airflow successfully meets the 40 mW/cm² cooling requirement,
This contribution presents the R&D trajectory of ITS3, from sensor physics and radiation qualification to air-cooling mechanics and final qualification prototype.
