Speaker
Description
For the High Luminosity upgrade of the Large Hadron Collider, the current ATLAS Inner Detector will be replaced by an all-silicon Inner Tracker (ITk). The installation is foreseen during the next LHC Long Shut Down 3 (2026-2030). The new tracker has been designed to face the challenging environment associated with the high number of collisions per bunch crossing and the expected large integrated luminosity. Therefore, ITk design has been optimized to maintain the current tracking performance but in such much more hostile environment. The ITk consists of a Pixel detector in the innermost part and a Strip detector in the outermost part. Both detectors are arranged in a central barrel section and two endcaps, to guarantee tracking hermeticity up to the very forward region of pseudorapidity 4.
Regarding the Pixel Detector, two different technologies have been chosen for the sensors: 3D and planar.
Due to their intrinsic radiation hardness, 3D pixel sensor have been chosen to instrument the innermost layer of the Pixel detector while the other layers will use planar sensors. Two pixel cells have been chosen according to the detector location: a 25x100 um2 rectangular cell for the barrel, and a 50x50 um2 squared cell for the end-cap, to optimize the ATLAS detector performance. The 3D sensors are produced by two vendors: Fondazione Bruno Kessler (FBK, Italy) and Stiftelsen for industriell og teknisk forskning (SINTEF, Norway). Each 3D sensor is hybridized to a readout chip to form the so-called single bare module, and three bare modules are then assembled by a flex circuit in a triplet module. This arrangement makes the 3D modules very different from the planar ones, in which a single large sensor tile is hybridized to four readout chips to form a quad module.
The 3D performance up to End of Lifetime (~1.7 10e16 neq/cm2) have been studied in R&D using preproduction parts on Single Chip Cards. Despite showing the excellent radiation hardness of the sensors, the main limitations of this approach have been the use of the readout chip ITkPixV1.1 that does not have the ability to read the ToT and the fact to test a single chip assembly only, rather than a final module. In this talk, we are showing for the first time results that overcome these limitations. We have built and tested in the laboratories triplet modules, thus formed by three single bare modules joint by a PCB, both with the preproduction readout ITkPixV1.1 and the production one, ITkPxV2. We have then irradiated few of them, at CERN IRRAD facility and at RARiS in Japan, and tested on a pion beam extracted by the CERN SPS.
We are therefore presenting for the first time the performance of these 3D triplet modules, in the final hardware configuration as they will be installed in the detector. We will present their efficiency as a function of the fluence and the charge collection as ITkPxV2 allows for the ToT measurement.
