Characterization of SABRE crystal NaI-33 with direct underground counting

4 Dec 2020  ·  M. Antonello, I. J. Arnquist, E. Barberio, T. Baroncelli, J. Benziger, L. J. Bignell, I. Bolognino, F. Calaprice, S. Copello, I. Dafinei, D. D'Angelo, G. D'Imperio, M. D'Incecco, G. Di Carlo, M. Diemoz, A. Di Giacinto, A. Di Ludovico, W. Dix, A. R. Duffy, E. Hoppe, A. Ianni, M. Iannone, L. Ioannucci, S. Krishnan, G. J. Lane, I. Mahmood, A. Mariani, S. Milana, J. Mould, F. Nuti, D. Orlandi, V. Pettinacci, L. Pietrofaccia, S. Rahatlou, F. Scutti, M. Souza, A. E. Stuchbery, B. Suerfu, C. Tomei, P. Urquijo, C. Vignoli, A. Wallner, M. Wada, A. G. Williams, A. Zani, M. Zurowski ·

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.

PDF Abstract
No code implementations yet. Submit your code now

Categories


Instrumentation and Detectors