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T: Fachverband Teilchenphysik

T 36: Neutrinoloser Doppelbeta-Zerfall II

T 36.9: Vortrag

Montag, 29. Februar 2016, 18:50–19:05, VMP9 SR 07

Suppression of the background coming from ⁴²Ar in the GERDA experiment — •Alexey Lubashevskiy for the GERDA collaboration — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg

The GERDA experiment aims at the 0νββ search in ⁷⁶Ge. The search is performed with high purity germanium detectors operated in liquid argon. 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. Several ways to suppress such background has been investigated. The tests were performed at LArGe low-background test facility, which gives a possibility to operate bare detectors in about 1m³ of LAr. It is equipped with a scintillation veto, so particles which deposit part of their energy in LAr can be detected by PMTs. The experimental setup is located at LNGS underground laboratory close to GERDA experiment location. Different experimental techniques were tested together with pulse shape discrimination (PSD) method in order to suppress ⁴²K background. The chosen solution for GERDA Phase II is so called "nylon mini-shroud" (NMS). It is made from nylon foil and covered with wavelength shifter from both sides. NMS allows to suppress collection of ⁴²K ions towards to the surface significantly. It was demonstrated in LArGe that together with PSD and scintillation veto the ⁴²K background can be suppressed in more than 1000 times. The results obtained during commissioning runs in GERDA Phase II will be also presented.