Aboveground antineutrino detection requires careful control of cosmogenic background sources and accurate quantification of any residual backgrounds that survive an Inverse Beta Decay (IBD) event selection. Cosmic high-energy neutrons are among the most prominent sources of background since their flux is relatively high at the Earth’s surface. The PROSPECT detector (Precision Reactor Oscillation and SPECTrum) was deployed at less than 10 m distance from the High Flux Isotope Reactor at Oak Ridge National Laboratory and has demonstrated successful aboveground antineutrino measurements with a signal-to-background ratio greater than 1:1. A detailed Monte Carlo simulation code was developed to match the performance of PROSPECT during the reactor off period when only residual backgrounds are measured. In addition to illuminating the characteristics of these residual backgrounds, this code allows us to examine the performance of a variety of notional shielding and detector configurations. In this work, we describe the performance of compact shielding configurations to provide input on cosmic neutron background reduction for future aboveground antineutrino detector designs.
This work is supported by the US DOE Office of High Energy Physics, the Heising-Simons Foundation, CFREF and NSERC of Canada, and internal investments at all institutions, and by the U.S. Department of Energy National Nuclear Security Administration and Lawrence Livermore National Laboratory [Contract No. DE-AC52-07NA27344, release number LLNL-ABS-832544].