One of the main goals of the ongoing upgrade of ALICE during the second long LHC shutdown
(LS2) is to significantly improve the charged particle tracking and secondary vertex reconstruction,
as well as the readout rate capabilities of the detector system. The ALICE physics programme of
measurements of low momentum charm and beauty hadrons and low-mass dielectrons in heavy-ion
collisions at the LHC requires the development of an entirely new Inner Tracking System (ITS2)
with the increased capabilities in readout speed, impact parameter resolution and the reduced
material budget. These requirements are met in the ITS2 design by the application of arrays of
novel coordinate-sensitive CMOS Monolithic Active Pixel Sensors (MAPS) with the sensor matrix
and readout integrated in a single chip, named ALPIDE (ALice PIxel DEtector). Besides MAPS,
large improvements of the tracking precision and efficiency of registration of particles with low
transverse momentum were achieved by a large reduction of the material budget of the ITS2 in
the region close to the interaction point. As a result, the record low level of 0.38% radiation length
(X/Xo) per layer for each of three innermost layers is achieved, ensuring the overall improved
efficiency for heavy-flavor measurements at low pT.
The first part of the talk is devoted to the general physics motivation, requirements and status of
the ITS2 preparations for the start of RUN3 at the LHC. The second part of the presentation will
cover new ideas of the ALICE upgrade during the next Long Shutdown 3 (LS3) in the period 2023-
2024 and the ongoing R&D on the development of a high granularity fast detector (ITS3) which
will further reduce the material to X/Xo below 0.05% per layer, will be presented. This will include
the concept of the ITS3, the status of very thin (∼20 μm) MAPS sensor developments as well as the
ongoing studies of the extra-light-weight mechanics and gas-cooling issues.
Acknowledgement: This work was partially supported by Funds of Ministry of Science and Higher
Education of the Russian Federation and by the National Research Center “Kurchatov Institute”.