/ physics.ins-det arXiv:1501.05762

LArGe - Active background suppression using argon scintillation for the GERDA $0\nu\beta\beta$-experiment

Agostini, M. (Munich, Tech. U.) ; Barnabé-Heider, M. (Heidelberg, Max Planck Inst.) ; Budjáš, D. (Munich, Tech. U.) ; Cattadori, C. (INFN, Milan) ; Gangapshev, A. (Moscow, INR) ; Gusev, K. (Kurchatov Inst., Moscow) ; Heisel, M. (Heidelberg, Max Planck Inst.) ; Junker, M. (Gran Sasso) ; Klimenko, A. (Dubna, JINR) ; Lubashevskiy, A. (Dubna, JINR) ; Pelczar, K. (Jagiellonian U.) ; Schönert, S. (Munich, Tech. U.) ; Smolnikov, A. (Dubna, JINR) ; Zuzel, G. (Jagiellonian U.)

Pages: 10

Abstract: LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for future application in the GERDA experiment. Similar to GERDA, LArGe operates bare germanium detectors submersed into liquid argon (1 m$^3$, 1.4 tons), which in addition is instrumented with photomultipliers to detect argon scintillation light. The scintillation signals are used in anti-coincidence with the germanium detectors to effectively suppress background events that deposit energy in the liquid argon. The background suppression efficiency was studied in combination with a pulse shape discrimination (PSD) technique using a BEGe detector for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times $10^3$ have been achieved. First background data of LArGe with a coaxial HPGe detector (without PSD) yield a background index of (0.12$-$4.6)$\cdot 10^{-2}$ cts/(keV$\cdot$kg$\cdot$y) (90% C.L.), which is at the level of GERDA Phase I. Furthermore, for the first time we monitor the natural $^{42}$Ar abundance (parallel to GERDA), and have indication for the $2\nu\beta\beta$-decay in natural germanium. These results show the effectivity of an active liquid argon veto in an ultra-low background environment. As a consequence, the implementation of a liquid argon veto in GERDA Phase II is pursued.

Web-Page: http://inspirehep.net/record/1340873/files/inside_cryostat.png; http://inspirehep.net/record/1340873/files/FADCscheme.png; http://inspirehep.net/record/1340873/files/cryostat_vm2000.png; http://inspirehep.net/record/1340873/files/LArGe_setup3D.png; http://inspirehep.net/record/1340873/files/arXiv:1501.05762.pdf

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