2025/10/02 by A. Sturniolo, Sturniolo, Alessandro
Engineering · Physics and Astronomy · #FOS: Physical sciences #Instrumentation and Detectors (physics.ins-det) #Magnetic Field Sensors Techniques #Particle Detector Development and Performance #Radiation Detection and Scintillator Technologies
paper · pdf · doi:10.48550/arxiv.2510.01834
openalex publication_date 2025/10/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
During the Long Shutdown 3 (LS3, scheduled 2026-2030), the innermost 3 layers (Inner Barrel, or IB) of the present ALICE ITS2 will be replaced with large-area, flexible, stitched CMOS 65 nm sensors, arranged in 2 half-barrels of 3 half-layers each, in the framework of the ITS3 upgrade project. For the first time in a High Energy Physics experiment, such large-scale sensors will be bent into truly half-cylindrical shaped half-layers, requiring little mechanical support. This will also help lower the material budget: a reduction down to an average of 0.09% X0 per layer is expected, benefitting ITS tracking and vertexing capabilities especially at low momenta. In the wafer yield and stitching assessment stage for ITS3 R&D, test devices from the Engineering Run 1 (ER1) submission were developed, including the MOnolithic Stiched Sensors (MOSS) and smaller variants of them (babyMOSS). In particular, babyMOSS is a single Repeated Sensor Unit (RSU) of a MOSS device: the chip is ∼14×30 mm2 in size, and consists of 8 digitally read out pixel matrices (regions) arranged in 2 rows, i.e. half-units (HUs). BabyMOSS chip characterisation tests have been performed in laboratory and test beam environments. Laboratory tests include systematic functional scans to study the behaviour of front-end electronics over a range of different settings, whereas test beam measurements, under high-energy charged particle beams, were used to investigate the detection efficiency and spatial resolution. In this contribution, we will present the babyMOSS chip characterisation campaign, with a focus on recent test beam results. So far, babyMOSS test beam results have been consistent with full MOSS, and confirmed that babyMOSS devices meet the ITS3 requirements: a detection efficiency >99%, fake hit rate <10-6 hits per pixel and event, and a spatial resolution <6 μm.