GERDA phase II detectors: Behind the production and characterisation at low background conditions

The low background GERmanium Detector Array (GERDA) at Laboratori Nazionali del Gran Sasso (LNGS) is designed to search for the rare neutrinoless double beta decay (0νββ) in 76Ge⁠. Bare germanium diodes are operated in liquid argon which is used as coolant, as passive and soon active as well shield against external radiation. Currently, Phase I of the experiment is running using ∼15 kg of co-axial High Purity Germanium diodes. In order to increase the sensitivity of the experiment 30 Broad Energy Germanium (BEGe) diodes will be added within 2013. This presentation reviews the production chain of the new BEGe detectors from isotopic enrichment to diode production and testing. As demonstrated all steps were carefully planned in order to minimize the exposure of the enriched germanium to cosmic radiation. Following this premise, acceptance and characterisation measurement of the newly produced diodes have been performed within the HEROICA project in the Belgian underground laboratory HADES close to the diode manufacturer. The test program and the results from a subset of the recently terminated GERDA Phase II BEGe survey will be presented.