Speaker
Description
[Submitted on behalf of ATLAS ITk collaboration]
For the High-Luminosity upgrade of the Large Hadron Collider, the existing ATLAS Inner Detector will be replaced with a fully silicon-based Inner Tracker (ITk). Its installation is planned for the next LHC Long Shutdown 3 (2026–2030). The ITk has been specifically designed to withstand the demanding conditions created by the high collision rates per bunch crossing and the large integrated luminosity expected in this new phase. To address these challenges, the design has been optimized to preserve the current tracking performance despite the far harsher environment. The ITk is composed of a Pixel detector at the innermost region and a Strip detector in the outer region. Both subsystems are organized into a central barrel and two endcap regions, providing nearly hermetic tracking coverage up to a pseudorapidity of η = 4, thereby ensuring efficient reconstruction even in the very forward regions.
For the Pixel Detector, two sensor technologies have been adopted: 3D and planar. Owing to their superior intrinsic radiation hardness, 3D pixel sensors have been selected for the innermost layer of the Pixel Detector, while planar sensors are employed in the outer layers. The pixel cell geometry has been optimized according to the detector region: rectangular cells of 25×100𝜇m2 are used in the barrel, whereas square cells of 50×50𝜇m2 are implemented in the end-cap, in order to maximize the overall tracking performance of ATLAS. The 3D sensors are fabricated by two vendors: Fondazione Bruno Kessler (FBK, Italy) and Stiftelsen for INdustriell og TEknisk Forskning (SINTEF, Norway), and the planar sensors by FBK, Micron Technology (Micron, USA) and Hamamatsu Photonics K.K. (HPK, Japan). Each 3D sensor is hybridized with a single readout chip to form a bare module; subsequently, three bare modules are interconnected via a flex circuit to create a triplet module. This design contrasts with the planar technology, where a single large sensor tile is hybridized to four readout chips to produce a quad module.
The detector performance up to the expected end-of-lifetime fluences (~1.7x10e16 neq/cm2 for 3D and 5x10e15 neq/cm2 for planar) has been investigated in R&D studies using pre-production devices assembled on Single Chip Cards. While these studies demonstrated the excellent intrinsic radiation hardness of both sensor technologies, the main limitation was that only single-chip assemblies were tested, rather than complete detector modules. In this talk, we report on the performance of detector modules in their final hardware configuration, as they will be deployed in ATLAS. For this purpose, triplet modules—comprising of three 3D bare modules connected together in a PCB—and quad modules—comprising of a planar quad bare module connected in a PCB—were built and tested. Both module types were equipped with the production ITkPixV2 readout chips. Assembly and quality control procedures were carried out at ATLAS-qualified production and testing sites. A subset of these modules was subsequently irradiated at the CERN IRRAD facility and at RARiS (Japan). Pre- and post-irradiation performance was tested using a pion beam extracted from the CERN SPS. The collected data were analyzed with the Corryvreckan software framework to evaluate the detector efficiency. Results are presented as a function of fluence, bias voltage, threshold settings, and charge collection, the latter benefiting from the Time-over-Threshold (ToT) measurement capability of ITkPixV2.
| Position | Postdoc |
|---|---|
| Affiliation | Institut de Física d'Altes Energies (IFAE), Barcelona |
| Country | Spain |