Detector optimization to reduce the cosmogenic neutron backgrounds in the TAO experiment

TL;DR

This paper presents detector optimization strategies, including material doping and shielding enhancements, to significantly reduce cosmogenic neutron backgrounds in the TAO experiment, thereby improving measurement accuracy.

Contribution

It introduces specific measures such as Gadolinium doping, shielding modifications, and veto strategy optimization to lower neutron backgrounds in shallow overburden neutrino detectors.

Findings

Neutron background reduced from 10% to 2% of signals.

Shielding and doping strategies effectively suppress background.

Potential for further background suppression with pulse shape discrimination.

Abstract

Short-baseline reactor antineutrino experiments with shallow overburden usually have large cosmogenic neutron backgrounds. The Taishan Antineutrino Observatory (TAO) is a ton-level liquid scintillator detector located at about 30 m from a core of the Taishan Nuclear Power Plant. It will measure the reactor antineutrino spectrum with high precision and high energy resolution to provide a reference spectrum for JUNO and other reactor antineutrino experiments, and provide a benchmark measurement to test nuclear databases. Background is one of the critical concerns of TAO since the overburden is just 10 meter-water-equivalent. The cosmogenic neutron background was estimated to be ~10% of signals. With detailed Monte Carlo simulations, we propose several measures in this work to reduce the neutron backgrounds, including doping Gadolinium in the buffer liquid, adding a polyethylene layer above the bottom lead shield, and optimization of the veto strategy. With these improvements, the neutron background-to-signal ratio can be reduced to ~2%, and might be further suppressed with pulse shape discrimination.