학술논문
Characterization of SABRE crystal NaI-33 with direct underground counting
Document Type
article
Author
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
Source
European Physical Journal C: Particles and Fields, Vol 81, Iss 4, Pp 1-11 (2021)
Subject
Language
English
ISSN
1434-6044
1434-6052
1434-6052
Abstract
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 $$^{39}$$ 39 K contamination of 4.3 ± 0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1 ± 0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of $$^{226}$$ 226 Ra and $$^{228}$$ 228 Th inside the crystal to be $$5.9\pm 0.6~\upmu $$ 5.9 ± 0.6 μ Bq/kg and $$1.6\pm 0.3~\upmu $$ 1.6 ± 0.3 μ Bq/kg, respectively, which would indicate a contamination from $$^{238}$$ 238 U and $$^{232}$$ 232 Th at part-per-trillion level. We measured an activity of 0.51 ± 0.02 mBq/kg due to $$^{210}$$ 210 Pb out of equilibrium and a $$\alpha $$ α quenching factor of 0.63 ± 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.