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Article
Title	ITS3, the ALICE Vertex Detector for LHC Run 4
Author(s)	Krizek, Filip (Rez, Nucl. Phys. Inst.)
Collaboration	ALICE Collaboration
Publication	2024
Number of pages	7
In:	PoS VERTEX2023 (2024) 033
In:	32nd International Workshop on Vertex Detectors (VERTEX 2023), Sestri Levante, Italy, 16 - 20 Oct 2023, pp.033
DOI	10.22323/1.448.0033
Subject category	Detectors and Experimental Techniques ; Particle Physics - Experiment ; Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ALICE
Abstract	During LHC Long Shutdown 3 (2026–2028), the ALICE Collaboration plans to upgrade the innermost layers of the current Inner Tracking System detector (ITS) with a novel vertex detector ITS3. The concept of this new vertex detector is based on ultra-thin ($< 50 \mu$m), wafer-scale (up to about $10 \times 26$ cm$^{2}$ large) Monolithic Active Pixel Sensors (MAPS) that are fabricated using the 65 nm CMOS process. Such sensors can be bent to radii as small as 18 mm and can be utilized to construct truly cylindrical-detector shells with an unprecedently low material budget, 0.05% 𝑋$_0$ per layer only. The development of this detector includes a number of cutting-edge R&D; efforts, including the qualification of MAPS in 65 nm, the development of wafer-scale stitched MAPS, the concept of bent MAPS, ultra-light mechanics based on carbon foam supports, and air cooling. This contribution provides 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 production of the first MOnolithic Stitched Sensor (MOSS).
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