[en] 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 m³, 1.4tons), which in addition is instrumented with photomultipliers to detect argon scintillation light. The light is 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 10³ have been achieved. First background data of LArGe with a coaxial HPGe detector (without PSD) yield a background index of the order 10⁻² cts/(keV-kg-y), which is at the level of the GERDA phase I design goal. As a consequence of these results, the development of an active liquid argon veto in GERDA is pursued.

[en] The viability of producing BEGe-type detectors from isotopically modified germanium for the neutrinoless double beta decay experiment GERDA is demonstrated by a complete test of the supply chain.

[en] The GERDA experiment searches for the neutrinoless double beta (0νββ) decay of ⁷⁶Ge using high-purity germanium detectors made of material enriched in ⁷⁶Ge. For Phase II of the experiment a sensitivity for the half life T_1/2^0ν ∼ 2·10²⁶ yr is envisioned. Modified Broad Energy Germanium detectors (BEGe) with thick n⁺ electrodes provide the capability to efficiently identify and reject background events, while keeping a large acceptance for the 0νββ-decay signal through novel pulse-shape discrimination (PSD) techniques. The viability of producing thick-window BEGe-type detectors for the GERDA experiment is demonstrated by testing all the production steps from the procurement of isotopically modified germanium up to working BEGe detectors. Comprehensive testing of the spectroscopic as well as PSD performance of the GERDA Phase II prototype BEGe detectors proved that the properties of these detectors are identical to those produced previously from natural germanium material following the standard production line of the manufacturer. Furthermore, the production of BEGe detectors from a limited amount of isotopically modified germanium served to optimize the production, in order to maximize the overall detector mass yield. The results of this test campaign provided direct input for the subsequent production of the enriched germanium detectors.