  During the era of the High Luminosity LHC (HL-LHC) the devices in its
experiments will be subjected to increased radiation levels with high fluxes of
neutrons and charged hadrons, especially in the inner detectors. A systematic
program of radiation tests with neutrons and charged hadrons is being carried
out by the CMS and ATLAS Collaborations in view of the upgrade of the
experiments, in order to cope with the higher luminosity at HL-LHC and the
associated increase in the pile-up events and radiation fluxes. In this work,
results from a complementary radiation study with $^{60}$Co-$\gamma$ photons
are presented. The doses are equivalent to those that the outer layers of the
silicon tracker systems of the two big LHC experiments will be subjected to.
The devices in this study are float-zone oxygenated p-type MOS capacitors. The
results of CV measurements on these devices are presented as a function of the
total absorbed radiation dose following a specific annealing protocol. The
measurements are compared with the results of a TCAD simulation.
