Study of Silicon Photomultiplier Radiation Hardness with Proton Beam from the JULIC Cyclotron

In this work we study the performance of silicon photomultiplier (SiPM) light sensors after exposure to the JULIC cyclotron proton beam, of energy $\sim$ 39 MeV, relative to their performance before exposure. The SiPM devices used in this study show a significant change in their behavior and downward shift of their breakdown voltage by as much as $\sim$ 0.4$\pm$0.1 V. Single photon measurements appear to be no longer possible for the SiPMs under study after exposure to a dose of $\sim$ 0.2 Gy (corresponding to an integrated proton flux of $\sim$$\phi_{p}$=1.06x10$^{8}$ p/cm$^{2}$). No visible damage to the surface of the devices was caused by the exposure.