Study of the light production mechanism of epoxy resins in an electric field

During the commissioning of the Double Chooz experiment light signals not related to light leaks were detected by the photomultiplier tubes. A specific study of the so-called light noise has been carried out, and it has been found that an emission of light could be produced by the epoxy covering the photomultiplier base circuit under certain conditions of high voltage and temperature. Several tests have been carried out in laboratory with different resins, which evidenced the emission of light pulses through a corona effect and the relationship of the rate and amplitude of the light pulses with temperature and high voltage across the base circuit. The results of these investigations can be particularly relevant for several other neutrino experiments that are known to use similar optical units and base assembly.