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

Nastasi, M.; Paonessa, A.; Previtali, E.; Quadrivi, E.; Sisti, M.; Aiello, S.; Andronico, G.; Antonelli, V.; Baldini, W.; Bellato, M.; Bergnoli, A.; Brigatti, A.; Brugnera, R.; Budano, A.; Buscemi, M.; Cammi, A.; Caruso, R.; Chiesa, D.; Clementi, C.; Corti, D.; Costa, S.; Dal Corso, F.; Ding, X. F.; Dusini, S.; Fabbri, A.; Fiorentini, G.; Ford, R.; Formozov, A.; Galet, G.; Garfagnini, A.; Giammarchi, M.; Giaz, A.; Grassi, M.; Isocrate, R.; Landini, C.; Lippi, I.; Lombardi, P.; Malyshkin, Y.; Mantovani, F.; Mari, S. M.; Marini, F.; Martellini, C.; Martini, A.; Meroni, E.; Mezzetto, M.; Miramonti, L.; Montini, P.; Montuschi, M.; Ortica, F.; Paoloni, A.; Parmeggiano, S.; Pelliccia, N.; Ranucci, G.; A. C., Re; Ricci, B.; Romani, A.; Saggese, P.; Salamanna, G.; Sawi, F. H.; Serafini, A.; Settanta, G.; Sirignano, C.; Stanco, L.; Strati, V.; Tuvè, C.; Verde, G.; Votano, L.

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.