Effects of very high radiation on SiPMs

Abstract During the last 5 years we have successfully completed R&D for the instrumentation of silicon photo multipliers (SiPMs) for the CMS HCAL Phase 1 upgrade in 2018. Much focus was put on radiation damage during these years. For the HCAL we expect a maximum total dose of 10 12  n/cm 2 for a total lifetime integrated luminosity of 3000 fb −1 . Good correlation between cell size and performance with high radiation was found during this R&D. To evaluate the possibility of using the SiPMs in the wider CMS environment we have exposed the current state of the art smallest cell SiPMs to radiation of 6×10 12  p/cm 2 in 62 MeV LIF beam line in 2014 at UCL Belgium and up to 1.3×10 14  p/cm 2 in the CERN PS 23 GeV proton beam in late 2014. The SiPM׳s main parameters were measured before and after irradiation. Here we report on the effects of noise increase and breakdown voltage shift due to the extremely high dose.