Neutron Damage of ATLAS Endcap Alignment CCDs

The endcap alignment system of the muon spectrometer of the ATLAS detector uses TC255P image sensors, which are charge-coupled devices (CCDs). Exposure to neutron irradiation in ATLAS can damage these CCDs. This damage can be measured by observing dark current, defined as a flow of thermally generated electrons into pixels. In this study, we measure the dark current present in the ATLAS endcap muon alignment CCDs and we obtain a proportionality constant (α) between measured dark current and total neutron dose received by each CCD throughout the ATLAS detector, where the total neutron dose is taken from neutron flux simulations generated by FLUGG and GEANT4. These results are compared to the values of α obtained from controlled experiments conducted at UMass Lowell and PROSPER0 reactor where CCDs are exposed to known neutron doses. We also investigate the effects of neutron energy spectra and the effects of CCD annealing in ATLAS over 2.5 years.