학술논문
Characterization of SABRE crystal NaI-33 with direct underground counting
Document Type
Working Paper
Author
Antonello, M.; Arnquist, I. J.; Barberio, E.; Baroncelli, T.; Benziger, J.; Bignell, L. J.; Bolognino, I.; Calaprice, F.; Copello, S.; Dafinei, I.; D'Angelo, D.; D'Imperio, G.; D'Incecco, M.; Di Carlo, G.; Diemoz, M.; Di Giacinto, A.; Di Ludovico, A.; Dix, W.; Duffy, A. R.; Hoppe, E.; Ianni, A.; Iannone, M.; Ioannucci, L.; Krishnan, S.; Lane, G. J.; Mahmood, I.; Mariani, A.; Milana, S.; Mould, J.; Nuti, F.; Orlandi, D.; Pettinacci, V.; Pietrofaccia, L.; Rahatlou, S.; Scutti, F.; Souza, M.; Stuchbery, A. E.; Suerfu, B.; Tomei, C.; Urquijo, P.; Vignoli, C.; Wallner, A.; Wada, M.; Williams, A. G.; Zani, A.; Zurowski, M.
Source
Eur. Phys. J. C 81, 299 (2021)
Subject
Language
Abstract
Ultra-pure NaI(Tl) crystals are the key element for a model-independent verification of the long standing DAMA result and a powerful means to search for the annual modulation signature of dark matter interactions. The SABRE collaboration has been developing cutting-edge techniques for the reduction of intrinsic backgrounds over several years. In this paper we report the first characterization of a 3.4 kg crystal, named NaI-33, performed in an underground passive shielding setup at LNGS. NaI-33 has a record low $^{39}$K contamination of 4.3$\pm$0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1$\pm$0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of $^{226}$Ra and $^{228}$Th inside the crystal to be $5.9\pm0.6 \mu$Bq/kg and $1.6\pm0.3 \mu$Bq/kg, respectively, which would indicate a contamination from $^{238}$U and $^{232}$Th at part-per-trillion level. We measured an activity of 0.51$\pm$0.02 mBq/kg due to $^{210}$Pb out of equilibrium and a $\alpha$ quenching factor of 0.63$\pm$0.01 at 5304 keV. We illustrate the analyses techniques developed to reject electronic noise in the lower part of the energy spectrum. A cut-based strategy and a multivariate approach indicated a rate, attributed to the intrinsic radioactivity of the crystal, of $\sim$1 count/day/kg/keV in the [5-20] keV region.