Performance of bare high-purity germanium detectors in liquid argon for the GERDA experiment

TL;DR

This paper reports on the first evaluation of bare high-purity germanium detectors operating in liquid argon, demonstrating their stability and suitability for use in the GERDA neutrinoless double beta decay experiment.

Contribution

It presents the first comprehensive study of the performance and stability of bare HPGe detectors in liquid argon for the GERDA experiment.

Findings

Detectors operated successfully in liquid argon

Performance remained stable over long-term measurements

Leakage currents were extensively characterized under gamma irradiation

Abstract

The GERmanium Detector Array, GERDA, will search for neutrinoless double beta decay in 76Ge at the National Gran Sasso Laboratory of the INFN. Bare high-purity germanium detectors enriched in 76Ge will be submerged in liquid argon serving simultaneously as a shield against external radioactivity and as a cooling medium. In GERDA Phase-I, reprocessed enriched-Ge detectors, which were previously operated by the Heidelberg-Moscow and IGEX collaborations, will be redeployed. Before operating the enriched detectors, tests are performed with non-enriched bare HPGe detectors in the GERDA underground Detector Laboratory to test the Phase-I detector assembly, the detector handling protocols, the refurbishment technology and to study the long-term stability in liquid argon. The leakage currents in liquid argon and liquid nitrogen have been extensively studied under varying gamma irradiation conditions. In total three non-enriched high-purity p-type prototype germanium detectors have been operated successfully. The detector performance is stable over the long-term measurements. For the first time, performance of bare high-purity germanium detectors in liquid argon is reported.