Journal Article

Neutron-induced background in the CONUS experiment

Fülber, K, Zbořil, M, Klages, T, Wink, R, Rink, T, Maneschg, W, Solasse, D, Strecker, H, Zimbal, A, Schierhuber, T, Heusser, G, Buck, C, Hakenmüller, J, Reginatto, M, Lindner, M, Lücke, A

2019

Overview

CONUS is a novel experiment aiming at detecting elastic neutrino–nucleus scattering in the almost fully coherent regime using high-purity germanium (Ge) detectors and a reactor as antineutrino source. The detector setup is installed at the commercial nuclear power plant in Brokdorf, Germany, at a short distance to the reactor core to guarantee a high antineutrino flux. A good understanding of neutron-induced backgrounds is required, as the neutron recoil signals can mimic the predicted neutrino interactions. Especially events correlated with the reactor thermal power are troublesome. On-site measurements revealed such a correlated, highly thermalized neutron field with a maximum fluence rate of \\[(745\\pm 30)\\,\\hbox {cm}^{-2}\\,\\hbox {day}^{-1}\\]. These neutrons, produced inside the reactor core, are reduced by a factor of \\[\\sim 10^{20}\\] on their way to the CONUS shield. With a high-purity Ge detector without shield the \\[\\gamma \\]-ray background was examined including thermal power correlated \\[^{16}\\hbox {N}\\] decay products and neutron capture \\[\\gamma \\]-lines. Using the measured neutron spectrum as input, Monte Carlo simulations demonstrated that the thermal power correlated field is successfully mitigated by the CONUS shield. The reactor-induced background contribution in the region of interest is exceeded by the expected signal by at least one order of magnitude assuming a realistic ionization quenching factor.

• Publisher: Springer Nature B.V
• Subject: Background radiation / Coherent scattering / Computer simulation / Correlation analysis / Elastic scattering / Fluence / Germanium / Neutrinos / Neutron flux / Nuclear capture / Nuclear power plants / Purity / Recoil / Thermoelectricity