Radiation hard pixel '3D' sensors for use in ATLAS-ITk at LHC

In preparation for operation at the High Luminosity LHC, the tracking system of the ATLAS experiment is replaced with a new inner tracker, the ITk. The innermost layers of this system must be designed to withstand a fluence of more than 10^16 cm-2 1 MeV neutron equivalents. At SINTEF, Norway, silicon pixel sensors have been produced in ‘3D’ design to tolerate such high fluences. Some of these sensors have been mounted with prototype readout electronics designed for operation at the ITk, the RD53A chip. The assembled modules have been shown to operate according to expectation in proton and electron test beams at CERN and DESY. Assemblies have subsequently been irradiated with protons up to a fluence of 5 x 10 ^15 protons cm-2 as well as with neutrons at a fluence of 10^16 cm- 2 . Subsequent beam tests show that the sensors can operate after such fluences with good efficiency. Results from these tests are presented.