The Novel ALICE Inner Tracking System (ITS3) Based on Truly Cylindrical, Wafer-Scale Monolithic Active Pixel Sensors

ALICE is studying replacing its innermost tracking layers during the LHC Long Shutdown 3 with a novel detector that will be as close as 18 mm to the interaction point and will have a target thickness of below 0.05% X0 per layer. To achieve these figures, a wafer-scale Monolithic Active Pixel Sensor in 65 nm technology is being developed. The sensors, fabricated on 300 mm wafers, will reach dimensions of up to 280 × 94 mm. They will subsequently be thinned down to values where they become flexible and are bent into truly cylindrical half-barrels. This paper outlines the detector concept and the R&D; progress. In particular, the first results from laboratory and beam tests with bent sensors are presented.