System upgrade for $\mu$Bq/m$^3$ level $^{222}$Rn concentration measurement

TL;DR

This paper presents a highly sensitive radon detection system capable of measuring $^{222}$Rn concentrations at the micro-Becquerel per cubic meter level, crucial for reducing background in underground neutrino experiments.

Contribution

The development of a novel $^{222}$Rn measurement system using activated carbon enrichment and electrostatic detection at unprecedented sensitivity levels.

Findings

Measured adsorption coefficients under various conditions.

Analyzed effects of temperature, flow rate, and radon concentration on detection efficiency.

Demonstrated system sensitivity at the $$ Bq/m$^3$ level.

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multipurpose underground liquid scintillator detector, was proposed for the determination of the neutrino mass hierarchy as primary physics goal. The central detector will be submerged in a water Cherenkov detector to lower the background from the environment and cosmic muons. Radon is one of the primary background sources. Nitrogen will be used in several sub-systems, and a highly sensitive radon detector has to be developed to measure its radon concentration. A system has been developed based on $^{222}$Rn enrichment of activated carbon and $^{222}$Rn detection based on the electrostatic collection. This paper presents the detail of a $\mu$Bq/m$^3$ level $^{222}$Rn concentration measurement system and gives detailed information about how the adsorption coefficient was measured and how the temperature, flow rate, and $^{222}$Rn concentration affect the adsorption coefficient.