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T: Fachverband Teilchenphysik

T 65: Niederenergie-Neutrinophysik 3

T 65.4: Talk

Tuesday, March 25, 2014, 17:35–17:50, P106

⁴²K background mitigation for GERDA Phase II — •Alexey Lubashevskiy for the GERDA collaboration — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany

GERDA is a low background experiment aimed for the neutrinoless double beta decay search. The search is performed using high purity germanium detectors operated in liquid argon (LAr). One of the most dangerous backgrounds in GERDA is the background from ⁴²K which is a daughter isotope of cosmogenically produced ⁴²Ar presented in natural argon. ⁴²K ions collect on the surface of the detector and increase its background level. Developments of the suppression methods of such kind of background were performed at LArGe low-background test facility, which gives a possibility to operate bare detectors in about 1 m³ of LAr. It is equipped with scintillation veto, so particles which deposit part of their energy in LAr can be detected by 9 PMTs. It is located at LNGS underground laboratory close to GERDA experiment. In order to better understand background and to increase statistics the LAr of LArGe was spiked with specially produced ⁴²Ar. Different experimental techniques were tested together with pulse shape dicrimination method and PMT veto in order to suppress ⁴²K background. Obtained results show a possibility to suppress the background below the requirements for GERDA Phase II.