Speaker: Chloe Ransom
Abstract: Many extensions of the Standard Model explain the dominance of matter over antimatter in our Universe by neutrinos being their own anti-particles. This would imply that a lepton number violating radioactive decay named neutrinoless double beta (0???) decay exists, whose detection requires the upmost suppression of background. The Gerda collaboration searches for 0??? decay of Ge76 by operating bare germanium detectors, enriched in Ge76, in liquid argon. The Gerda experiment has instrumented the liquid argon (LAr) around the detecotr array with photomultiplier tubes (PMTs) for the readout of scintillation light thereby providing an active LAr veto system for background events. The PMTs currently used are not sensitive to LAr scintillation light, and use wavelength shifting foil to shift the LAr scintillation light to their region of sensitivity. A new PMT with a magnesium fluoride (MgF2) window is transparent to the LAr scintillation light, and therefore does not require the wavelength shifting foil. Reduction of material is important for a zero-background experiment such as Gerda. I present a summary of measurements made so far with this PMT, including gain, dark current and afterpulses rate, at both room temperature and cooled with nitrogen. Future work will include long-term tests in LAr.