Germanium detector array — GERDA

GERDA will be a new experiment at the Laboratori Nazionali del Gran Sasso (LNGS) to study neutrinoless double beta decay of 76Ge at background levels <10−3 cts/(keV kg y) at Q β β = 2039 keV , two orders of magnitude lower than in the previous experiments. Bare Ge-diodes, enriched to 86% in 76Ge, are operated in liquid argon complemented by a water shield to reduce the external backgrounds. Intrinsic backgrounds will be suppressed by the pulse shape analysis and segmented electrodes. In GERDAs first phase, the detector array will consist of the existing and refurbished detectors of the previous Heidelberg–Moscow and IGEX experiments. After one year of measurement, the setup should allow us to scrutinize the claimed observation of 0 ν β β decay in 76Ge. In its second phase, GERDA will use an additional set of new enriched 76Ge crystals, as segmented or point contact detectors. After 100 kg y the sensitivity will be T 1 / 2 , 0 ν > 1.5 ⋅ 10 26 y ; this corresponds to an effective Majorana mass range from 0.1 eV to 0.2 eV.