Uniformity of the APD response after irradiation

In 10 years of operation in the CMS electromagnetic calorimeter (ECAL), avalanche photodiodes will be exposed to 1 MeV equivalent neutron fluence of 2middot10¹³ n/cm² and total ionization dose of 0.25 Mrad. These APDs are silicon photodiodes operated in avalanche mode. To explore the possibility of usage of these APDs in harsher radiation environments, they were irradiated with reactor neutrons up to 1 MeV equivalent fluence of 5middot10¹⁴ n/cm². This paper reports on measurements of current-voltage characteristics and scan of surface uniformity after irradiation.