Performance of radiation hard 3D pixel sensors for the upgrade of the ATLAS Inner Tracker

Abstract

The Inner Detector of the ATLAS experiment at CERN will be replaced by a completely new Inner Tracker (ITk) to exploit the performance of the High Luminosity upgrade of the LHC accelerator (HL-LHC). The new detector will have to operate in an unprecedented radiation environment. In particular, the hybrid pixel detectors of the innermost layer of the ITk will be exposed to a particle fluence of about 1.7 × 1016 neq/cm2 before being replaced. A novel 3D pixel sensor technology featuring thin active substrates and small pixel cells has been selected to instrument the innermost barrel layer and rings of the ATLAS ITk. Prototypes of 3D pixel sensors produced at CNM in Barcelona, Spain, including 3D pixelated test structures as well as half-size sensors coupled to the RD53A ASIC prototype for HL-LHC, have been irradiated with protons and neutrons up to the radiation doses expected for the innermost layers of ITk. Their performance in terms of leakage current, power dissipation and hit efficiency of different pixel geometries after irradiation have been investigated and compared to the requirements for ITk.