$^{222}$Rn contamination mechanisms on acrylic surfaces
M. Nastasi, A. Paonessa, E. Previtali, E. Quadrivi, M. Sisti, S. Aiello, G. Andronico, V. Antonelli, W. Baldini, M. Bellato, A. Bergnoli, A. Brigatti, R. Brugnera, A. Budano, M. Buscemi, A. Cammi, R. Caruso, D. Chiesa, C. Clementi, D. Corti
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.