Neutron temperature

Recoil

Neutron flux

Nuclear physics

Neutrino

Neutron

Physics

Neutron scattering

The European Physical Journal C

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.

Neutron-induced background in the CONUS experiment