Radiation damage in silicon photomultipliers exposed to neutron radiation

We studied performances of two SiPMs before and after irradiation at the Lubljana reactor. These high density (15 μ m cell pitch size) SiPMs were developed by Hamamatsu (in cooperation with the CMS SiPM group) for the CMS HCAL Upgrade Phase I project. The S10943-4732 is a photosensor selected for the CMS HE HCAL where the SiPMs will be exposed to 2× 10¹¹ n/cm² (1 MeV equivalent) for the operation time of the SLHC (integrated luminosity—5000 fb⁻¹). The HD-1015CN SiPM was developed using new Hamamatsu trench technology to reduce optical cross-talk (X-talk) between SiPM cells. Both SiPMs are considered as candidates for the CMS HCAL barrel upgrade. The SiPMs were irradiated with reactor neutrons up to 1 MeV equivalent fluence of 2× 10¹² n/cm² (that corresponds to the maximum integrated neutron fluence in the HCAL barrel for the duration of the SLHC operation).