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A 3 billion-pixel camera

The ALICE group at the Frascati National Laboratories has successfully completed its quota of the production of the new silicon pixel vertexing and tracking detector of the ALICE experiment at CERN.

The new ALICE Inner Tracking System (ITS2) is based on ultra-thin (50-100 microns) MAPS sensors using a 180 nm imaging CMOS technology. The ALICE LNF group has produced 27 staves (1/4 of the total basic linear units composing the ITS2 outer barrel) with a production yield of detector grade elements close to 97%. The production work started in mid 2016 and entered the regime in mid 2018. The workflow of the project was rather challenging due to the large number of critical tasks which had to be carried out. The stave construction steps include several hundred of high-precision, error prone steps that have to be executed with extreme accuracy.

The work was performed in a clean environment (clean rooms of ISO class 4 and 5) and in a dedicated infrastructure which was realized at the LNF with the help of the Technical Division.

The production rate between autumn 2018 and summer 2019 has reached almost 1 stave/week, also thanks to the dynamic reshuffling of tasks of the technical personnel which had acquired a large experience.

The produced modules have been sent to CERN for the final assembly of the outer barrel layers which are currently under commissioning. The installation of the ITS2 into ALICE is foreseen in mid 2020 while the global commissioning is set to start in autumn of the same year.

The excellent performance of the LNF ITS production site was made possible by the commitment and dedication of the technicians and engineers of both LNF Research and Technical division, coordinated by the ALICE LNF group. The Laboratory congratulates all of them!