A large, low-energy neutrino detector for neutrino oscillations and supernovae watch

Abstract

Abstract We describe a large, low-energy and low background Gd-loaded liquid scintillation detector with a fiducial mass of 1000 ton to be installed 200 m underground at a distance of 10–15 km from a power reactor. The detector will serve to explore neutrino oscillations down to mass parameters Δm2 of 10−4 eV2 and mixing angles sin22θ larger than 0.1 and also as a low-energy neutrino observatory for supernovae and other astrophysical events. The detector reaction νep → e+n provides a correlated e+, n signature with the neutron yielding an 8 MeV gamma cascade following capture in Gd. Some of the optimized parameters are: light transmission length 6.1 m, Gd concentration 0.05%, mean neutron capture time 46 μs. With thresholds for the positron kinetic energy and capture gamma rays of 1 and 3.5 MeV, respectively, we expect a detector efficiency of 50% and a signal rate of 16 neutrino events per day per 7.5 GW reactor power with a background rate of 2 per day. A 20 t prototype detector will serve for feasibility studies. Installed 1 km from a reactor it will be sensitive to mass parameters down to 10−3 eV2.