Development and Testing of a Detector to Study Neutrino Oscillations at Palo Verde

A detector for the study of neutrino oscillations with a projected sensitivity to Delta m^2 of 10^{-3} eV ^2 and to sin^2 2theta of 0.1 is described. It is to be installed 800 m from three pressurized water reactors at the Palo Verde Nuclear Generating Station near Phoenix, Arizona. The detector is segmented and filled with 12 tons of gadolinium-loaded liquid scintillator. It will be placed in an underground vault with an overburden of 46 mwe and surrounded by a 1-m-thick water buffer and a hermetic active muon veto. Reactor antineutrinos are detected through proton inverse beta decay in the hydrogen-rich scintillator, and the resulting positrons are discriminated from fast neutron background by requiring a prompt coincidence across several cells between the positron and its annihilation radiation. Test results from prototype detector elements are presented showing excellent stability of the scintillator and acrylic target cells. A method of calibrating the positron detection efficiency is described in detail, and results of a prototype experiment using a small-scale detector are presented. The results of a full-detector Monte Carlo simulation, based on the CERN and Oak Ridge packages GEANT and GCALOR, are discussed: anticipated backgrounds due to natural radioactivity and to fast neutrons are described in detail.