Low Radon Concentration Measurement with a Radon-Dissolved Liquid Scintillator Pilot Detector

TL;DR

This paper presents a novel low-radon detection method using a liquid scintillator dissolved radon detector, achieving high sensitivity and linear response for monitoring radon in nitrogen gas in rare-event search experiments.

Contribution

The study introduces a radon-dissolved liquid scintillator detector with cascade decay selection, providing a sensitive, linear, and optimized approach for radon measurement in nitrogen gas environments.

Findings

Background activity measured at 59.8±18.4 μBq per 300 mL LS

Radon concentration in LS is linearly related to nitrogen gas radon levels

Detection limit for 222Rn in nitrogen gas is 9.6 mBq/m^3

Abstract

We construct a high sensitivity radon pilot detector using liquid scintillator dissolved radon for the CDEX rare-event searches program. The CDEX-10 project employs a germanium detector array immersed in a massive liquid nitrogen tank. However, radon emanated from the surface of the tank can contribute background. As a result, radon contamination in the liquid nitrogen tank must be regulated and monitored, which necessitates the use of a low-level Rn measuring device. The radon-dissolved liquid scintillator (LS) detectors utilizes cascade decay selections, yielding a unique signature. All background events occurring in the LS, with regard to the system and co-efficiency of Rn absorption, have been studied. Background activity is measured to be 59.8$\pm$18.4 $\mu$Bq per 300 mL LS. Meanwhile, it shows that radon concentration absorbed by LS will be saturated and is linearly related to radon concentration in nitrogen gas. Furthermore, the co-efficiency factor can be optimized by lowering temperature or raising pressure. Eventually the detection limit for 222^Rn in nitrogen gas is observed to be 9.6 mBq/m^3.