Study of the radiation damage of silicon photomultipliers

Radiation damage significantly changes the performance of silicon photomultipliers (SiPM). In this work, we first have characterized KETEK SiPMs with a pixel size of 15 x 15 μm² using I-V (current-voltage), C/G-V/f (capacitance/impedance-voltage/frequency) and Q-V (charge-voltage) measurements with and without illumination with blue light of 470 nm from an LED. The SiPM parameters determined are DCR (dark count rate), relative PDE (photon detection efficiency), G (Gain), XT (cross-talk), Geiger breakdown characteristics, C_pix (pixel capacitance) and R_q (quenching resistance). Following this first characterization, the SiPMs were irradiated using reactor neutrons with fluences of 10⁹, 10¹⁰, 10¹¹, 5 . 10¹¹, and 10¹² n/cm². Afterwards, the same measurements were repeated, and the dependence of the SiPM parameters on neutron fluence was determined. The results are used to optimize the radiation tolerance of SiPMs.