The development of $^{222}$Rn detectors for JUNO prototype

TL;DR

This paper reports on the development of two high-sensitivity radon detectors based on water system prototypes for JUNO, capable of online monitoring of $^{222}$Rn to reduce background noise.

Contribution

It introduces two novel radon detection methods using Si-PIN photodiodes and liquid scintillators tailored for JUNO's water system.

Findings

Si-PIN Rn detector sensitivity ~9.0 mBq/m$^3$

Liquid scintillator Rn detector sensitivity ~64.0 mBq/m$^3$

Potential for online radon monitoring in JUNO detector system

Abstract

The radioactive noble gas $^{222}$Rn, which can be dissolved in water, is an important background source for JUNO. In this paper, based on the water system of JUNO prototype, two kinds of high sensitivity radon detectors have been proposed and developed. The sensitivity of Si-PIN Rn detector, which uses a Si-PIN photodiode to detect the $\alpha$ from $^{214}$Po decay, is $\sim$9.0~mBq/m$^3$. The sensitivity of LS Rn detector, which uses liquid scintillator to detect the coincident signals of $\beta$ from $^{214}$Bi decay and $\alpha$ from $^{214}$Po decay, is $\sim$64.0~mBq/m$^3$. Both of the two kinds of Rn detector have the potential to be developed as an online Rn concentration monitoring equipment for JUNO veto detector.