Speaker
Description
The ALICE collaboration is planning to install the next upgrade of the Inner Tracking System (ITS3) during the LHC Long Shutdown 3 (2026-2028). The aim of this upgrade is to reduce material budget of the three innermost layers from 0.3% of a radiation length $X_0$ to 0.05% $X_0$ per layer, essentially reducing it to the silicon contribution only. In order to achieve this, the layers of the current detector will be replaced with truly cylindrical layers made of wafer-scale, thin and flexible stitched CMOS pixel sensors.
These sensors, made using a 65 nm CMOS process and thinned down to less than 50 $\mu$m, will be flexible enough to form cylindrical shapes which will be installed at a distance of respectively 18, 24, and 30 mm from the interaction point.
In order to produce wafer-scale sensors a process called stitching is used to combine small reticles and build sensors up to 300 mm in length in a single wafer. This allows a full coverage of half of the cylindrical layer with only one module, with a total of 6 modules for the whole detector.
Thanks to the self supporting property of these modules the mechanical supports can be reduced to only carbon foam spacers. Furthermore, the power consumption of the sensors will stay below 20 mW/cm$^2$, enabling the use of forced air cooling. This upgrade will provide unprecedentedly good tracking and vertexing capabilities, improving the pointing resolution by a factor of 2 with respect to the current detector.
This contribution will provide an overview of the ALICE ITS3 detector and of the R&D achievements, including: the validation of the 65 nm technology for particle tracking and radiation hardness, the achievements in terms of bending and flexibility, the integration of wafer-scale silicon detectors, and the first production of stitched sensor prototypes.
| Collaboration / Activity | ALICE |
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