Large-size sub-keV sensitive germanium detectors for the CONUS experiment

TL;DR

The paper presents the development, commissioning, and operational performance of large, sub-keV sensitive germanium detectors used in the CONUS experiment to detect reactor antineutrinos via coherent elastic scattering.

Contribution

It introduces the design, fabrication, and successful deployment of four 1 kg germanium detectors with sub-keV thresholds for neutrino detection at a nuclear reactor.

Findings

Detectors achieved stable operation over two years.

Background levels were effectively minimized.

Excellent electronic performance was demonstrated.

Abstract

Intense fluxes of reactor antineutrinos offer a unique possibility to probe the fully coherent character of elastic neutrino scattering off atomic nuclei. In this regard, detectors face the challenge to register tiny recoil energies of a few keV at the maximum. The CONUS experiment was installed in 17.1 m distance from the reactor core of the nuclear power plant in Brokdorf, Germany, and was designed to detect this neutrino interaction channel by using four 1 kg-sized point contact germanium detectors with sub-keV energy thresholds. This report describes the unique specifications addressed to the design, the research and development, and the final production of these detectors. It demonstrates their excellent electronic performance obtained during commissioning under laboratory conditions as well as during the first two years of operation at the reactor site which started on April 1, 2018. It highlights the long-term stability of different detector parameters and the achieved background levels of the germanium detectors inside the CONUS shield setup.