Measurement of Radon-222 concentration in N2 using an activated charcoal trap

TL;DR

This paper presents a new activated charcoal trap for measuring Radon-222 in nitrogen gas, improving sensitivity for low-background experiments like dark matter detection and neutrino studies.

Contribution

Introduction of a novel activated charcoal trap with calibration methods to enhance Radon-222 detection sensitivity in nitrogen gas systems.

Findings

The trap's efficiency was characterized and optimized.

A radon calibration source was developed and tested.

The method improves Radon-222 detection sensitivity.

Abstract

Radon-222 is a limiting background in many leading dark matter and low energy neutrino experiments. One way to mitigate Radon-222 is to fill external experimental components with a clean cover gas such as N2. At the SNOLAB facility in Canada, the 222Rn concentration in the cover gas systems of the experiments are monitored using a radon assay board developed by the SNO collaboration. To improve the sensitivity of N2 assays, a new trapping mechanism based on activated charcoal has been developed. The trap was purified and tested at SNOLAB. The methods for determining the efficiency, background, and sensitivity of the trap were described. Additionally, as part of the efficiency measurement, a radon calibration source was developed and characterized.