  Pixel sensors in 3D technology equip the outer ends of the staves of the
Insertable B Layer (IBL), the innermost layer of the ATLAS Pixel Detector,
which was installed before the start of LHC Run 2 in 2015. 3D pixel sensors are
expected to exhibit more tolerance to radiation damage and are the technology
of choice for the innermost layer in the ATLAS tracker upgrade for the HL-LHC
programme. While the LHC has delivered an integrated luminosity of $\simeq$ 235
fb$^{-1}$ since the start of Run 2, the 3D sensors have received a non-ionising
energy deposition corresponding to a fluence of ${\simeq} 8.5\times10^{14}$ 1
MeV neutron-equivalent cm$^{-2}$ averaged over the sensor area. This paper
presents results of measurements of the 3D pixel sensors' response during Run 2
and the first two years of Run 3, with predictions of its evolution until the
end of Run 3 in 2025. Data are compared with radiation damage simulations,
based on detailed maps of the electric field in the Si substrate, at various
fluence levels and bias voltage values. These results illustrate the potential
of 3D technology for pixel applications in high-radiation environments.
