Characterisation of Hamamatsu Silicon Photomultiplier Arrays for the LHCb Scintillating Fibre Tracker Upgrade

In the context of the LHCb detector upgrade, during the long shutdown of LHC (2019/2020), the complete tracking system will be replaced to cope with the increased luminosity and trigger less readout scheme. A large area (300 $\mathrm {m^2}$ ) scintillating fibre tracker (SciFi) with more than 500 K channels and 250 $\mu $m readout pitch is under construction. The silicon photomultiplier used for the read-out provide high photon detection efficiency, low correlated noise (optical cross-talk and after-pulse), short recovery time and withstand a high neutron fluence. The Hamamatsu photo-detectors selected in November 2016 have been characterised before and after irradiation with neutrons and protons. We will focus on the study of the performance of these devices in the context of the LHCb SciFi application regarding the single photon detection capability after irradiation. New developed characterisation method will also be presented.