Comprehensive Study of Radon Progeny Attachment to Surfaces

TL;DR

This study investigates how radon progeny attach to various surfaces, affecting background noise in sensitive physics experiments, by analyzing over 1200 measurements and environmental factors to improve background estimation.

Contribution

It provides comprehensive measurements of radon progeny attachment rates on multiple materials and compares environmental influences and models, enhancing background prediction accuracy.

Findings

Attachment rates vary significantly with air exchange and surface potential.

Environmental parameters like temperature and humidity have limited impact.

Jacobi model's predictions are compared to experimental data.

Abstract

Low energy, low rate experiments, such as searches for neutrinoless double beta decay and dark matter, require unprecedentedly low levels of background in order to deliver their full science potential. $^{210}$Po driven, neutron induced background, caused by nuclear $(\alpha, n)$-reactions on low-Z materials, direct background contributions of the $^{210}$Po $\alpha$-radiation and desorption of the $^{210}$Pb progeny $^{210}$Bi from surfaces into the detector medium are of particular of concern. These backgrounds depend on details of the components' exposure to radon-loaded lab air and, thus, their handling history. The attachment rates of airborne radon progeny to surfaces, needed for the estimation of these background rates, are poorly understood. This article reports the results of a campaign comprising of more than 1200 attachment measurements, performed for 9 different materials. Correlations of the attachment with environmental parameters such as air exchange rate, electrical surface potential, temperature, atmospheric pressure, and relative humidity have been studied and found to be significant only in case of the first two. Attachment modelling, using the Jacobi model, is compared to data.