Radioactivity control strategy for the JUNO detector

TL;DR

The paper discusses the strategies implemented by the JUNO collaboration to minimize natural radioactivity backgrounds in their large liquid scintillator detector, ensuring the sensitivity needed for neutrino mass ordering studies.

Contribution

It presents a comprehensive approach combining optimized design, material screening, careful handling, and simulation to control radioactivity backgrounds in JUNO.

Findings

Background count rate kept below 10 Hz

Effective reduction of natural radioactivity sources

Validated strategies through Monte Carlo simulations

Abstract

JUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day, therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration to reduce at minimum the impact of natural radioactivity. We describe our efforts for an optimized experimental design, a careful material screening and accurate detector production handling, and a constant control of the expected results through a meticulous Monte Carlo simulation program. We show that all these actions should allow us to keep the background count rate safely below the target value of 10 Hz in the default fiducial volume, above an energy threshold of 0.7 MeV.