Effects of neutron irradiation on photomultiplier tubes and their power supplies

In the context of the Gamma-Flash program, whose objective is to investigate the emission of high-energy gamma rays and neutrons during thunderstorms, a neutron detection system, based on scintillators coupled to photomultiplier tubes, has been developed. The neutrons emitted are generated by photoproduction reactions in the atmosphere, and they have a wide range of energies, from MeV down to meV. In this work, the effects of neutron irradiation on photomultiplier tubes and their power supply are investigated to assess and quantify the effects of irradiation on dark count rate and during data acquisition. The detection system was irradiated at the ChipIr beamline at ISIS Neutron and Muon Source (UK).