Qualification of irradiated FBK 3D pre-production pixel sensors for the ATLAS ITk detector

With the beginning of the High Luminosity program of the Large Hadron Collider (HL-LHC) the ATLAS detector will have to face an increased instantaneous luminosity up to 7.5$\cdot$ 10$^{34}$ cm$^{-2}$ s$^{-1}$ and an average of 200 proton-proton collisions per bunch-crossing. To be ready for these challenging beam conditions the ATLAS Inner Detector will be completely replaced with a new all-silicon Inner Tracker, the ITk. The design phase of the ITk is concluding and the project is now moving into the pre-production phase. \par The ITk innermost layer will be exposed to a fluence up to 1.3$\cdot$10$^{16}$ n$_{eq}$/cm$^2$ at the half of the HL-LHC program, after which it is scheduled to be replaced. Sensors in the innermost layer need to be qualified up to a fluence of 2$\cdot$10$^{16}$ n$_{eq}$/cm$^2$ (with a 1.5 safety factor), hence 3D pixel sensors have been chosen to instrument it due to their radiation hardness. Sensors with 25x100~$\mu$m$^2$ pixel pitch will be used in the central region of the detector (Barrel) while sensors with a pitch of 50x50 $\mu$m$^2$ will instrument the two side regions (End-Caps). The Fondazione Bruno Kessler (FBK) has been chosen as one of the main vendors for the production of these sensors. \par This talk will present the qualification of 3D pre-production sensors with both pixel pitches produced by FBK, starting from laboratory characterization before irradiation up to performance measured in test beams with devices irradiated up to a fluence of 1.9$\cdot$10$^{16}$ n$_{eq}$/cm$^2$.