The High-Luminosity Large Hadron Collider (HL-LHC) will deliver instantaneous luminosities up to five times higher than those of the current LHC, reaching an unprecedented $7.5 \times 10^{34} \text{cm}^{-2}\text{s}^{-1}$. This significant increase in luminosity — resulting in an average pileup of over 200 interactions per bunch crossing — will pose serious challenges to existing detector systems. To maintain tracking performance under these conditions, the ATLAS Inner Detector (ID) will be replaced by an all-silicon Inner Tracker (ITk), providing coverage up to $|\eta| < 4$ and designed to withstand fluences up to $1.9 \times 10^{16}\,\text{n}_{\text{eq}}/\text{cm}^2$. The ITk will consist of five pixel layers and four strip layers in the barrel region. The innermost pixel layer will use triplet modules based on 3D silicon sensors, offering enhanced radiation hardness. The second layer will feature quad modules with $100 \mu \text{m}$ planar sensors, while the outer two layers will use quad modules with $150 \mu \text{m}$ planar sensors.
Testbeam activities are essential for characterizing the performance of ITk modules under the extreme conditions expected at the HL-LHC. In this talk, we will present results from the most recent testbeam campaigns conducted in 2024 and 2025 at the North Experimental Area at CERN. These measurements were carried out using a $120 \text{GeV/c}$ pion beam from the H6 beamline and a high-resolution Mimosa telescope for precise track reconstruction. A variety of module geometries were tested, including single-chip cards (SCC), quad, and triplet configurations, with particular focus on the performance of irradiated sensors. These results provide critical input for the final design validation and quality assurance processes ahead of large-scale production.
Among the tested modules was a 3D sensor from SINTEF featuring a new passivation method, irradiated to a fluence of $1.7 \times 10^{16}\,\text{n}_{\text{eq}}/\text{cm}^2$, which achieved an efficiency of $96\%$. Two planar sensors from FBK, irradiated to $0.5 \times 10^{16}\,\text{n}_{\text{eq}}/\text{cm}^2$, demonstrated efficiencies of approximately $99\%$. Other notable modules tested include an HPK quad module, a Micron SCC, and an FBK SCC, all equipped with an ITkPixV2, and two linear triplet modules—one produced by FBK and the other by SINTEF.
