In situ radiation damage studies of optoelectronics in the ATLAS SemiConductor Tracker

This paper presents results on in situ measurements of radiation damage for the on-detector optoelectronics for the ATLAS SemiConductor Tracker. The results come from proton-proton collisions in LHC during operation in 2016, 2017 and 2018. The results for both p - i - n diodes and VCSELs are given and compared to expectations from beam tests of devices from the same wafer, before the start of LHC operation. The VCSELs show evidence for some radiation damage as expected from earlier studies. The magnitude of the damage is compared with simple extrapolations from test beam data. The p - i - n diodes do show significant radiation damage as expected from test beam studies.