Low-background multi-HPGe spectrometer TGV II used for the study of double electron capture of 106Cd

The TGV II (Telescope Germanium Vertical) facility is a low background spectrometer operated in Modane Underground Laboratory (France). It aims at the study of double beta electron capture of 106Cd. The spectrometer is composed of 32 HPGe planar detectors (total mass of Ge ∼3 kg) interleaved with thin-foil samples made of enriched 106Cd. In 2007 the Phase I of the experiment (1 year measurement) was finished and the new limit on half-life for two-neutrino double electron capture (g.s. → g.s.) of 106Cd was obtained as 3.2 × 1020 years. This limit is significantly higher (by almost three orders of magnitude) than those already published. From December 2007 the Phase II of the experiment continues with more enriched material (13.6 grams instead of 8 grams) and with significantly suppressed background of the cryostat.