$^{222}$Rn contamination mechanisms on acrylic surfaces

TL;DR

This study investigates how $^{222}$Rn contamination occurs on acrylic surfaces, analyzing contamination mechanisms, depth, and diffusion to improve low-background experiment design.

Contribution

It provides new insights into $^{222}$Rn contamination processes on acrylic, including implantation depth and diffusion, based on experimental exposure and spectral analysis.

Findings

Contamination depth quantified through alpha spectra

Evidence of $^{222}$Rn diffusion inside acrylic

Decay mode analysis highlights contamination dynamics

Abstract

In this work, the $^{222}$Rn contamination mechanisms on acrylic surfaces have been investigated. $^{222}$Rn can represent a significant background source for low-background experiments, and acrylic is a suitable material for detector design thanks to its purity and transparency. Four acrylic samples have been exposed to a $^{222}$Rn rich environment for different time periods, being contaminated by $^{222}$Rn and its progenies. Subsequently, the time evolution of radiocontaminants activity on the samples has been evaluated with $\alpha$ and $\gamma$ measurements, highlighting the role of different decay modes in the contamination process. A detailed analysis of the alpha spectra allowed to quantify the implantation depth of the contaminants. Moreover, a study of both $\alpha$ and $\gamma$ measurements pointed out the $^{222}$Rn diffusion inside the samples.