Measurements of the radiation damage to the ITkPixV1 chip in X-ray irradiations

The upgrade of the ATLAS Inner Tracker (ITk) requires a pixel readout chip that can withstand the harsh environment of HL-LHC, with a peak luminosity of $5 \times 10^{34}$ cm$^{-1}$s$^{-1}$ and an estimated total ionising dose (TID) of around 1 Grad. The ITkPixV1 chip is the latest readout chip prototype for the ITk pixel upgrade. The radiation tolerance of this chip has been measured experimentally in irradiation campaigns using X-rays. The chip utilises a large number of digital cells in the chip logic, and the radiation damage to these cells is characterised by considering ring oscillator gate delays. The analog front-end is studied by tuning the chip thresholds before and after irradiation. Both the digital and analog logic show no operational issues after irradiation to 1 Grad (at a dose rate of 4 Mrad/h).