Performance of the SABRE detector module in a purely passive shielding

Abstract

We present here a characterization of the low background NaI(Tl) crystal NaI-33 based on a period of almost one year of data taking (891 kgxdays exposure) in a detector configuration with no use of organic scintillator veto. This remarkably radio-pure crystal already showed a low background in the SABRE Proof-of-Principle (PoP) detector, in the low energy region of interest (1-6 keV) for the search of dark matter interaction via the annual modulation signature. As the vetoable background components, such as ${}^{40}$K, are here sub-dominant, we reassembled the PoP setup with a fully passive shielding. We upgraded the selection of events based on a Boosted Decision Tree algorithm that rejects most of the PMT-induced noise while retaining scintillation signals with > 90% efficiency in 1-6 keV. We find an average background of 1.39 $\pm$ 0.02 counts/day/kg/keV in the region of interest and a spectrum consistent with data previously acquired in the PoP setup, where the external veto background suppression was in place. Our background model indicates that the dominant background component is due to decays of ${}^{210}$Pb, only partly residing in the crystal itself. The other location of ${}^{210}$Pb is the reflector foil that wraps the crystal. We now proceed to design the experimental setup for the physics phase of the SABRE North detector, based on an array of similar crystals, using a low radioactivity PTFE reflector and further improving the passive shielding strategy, in compliance with the new safety and environmental requirements of Laboratori Nazionali del Gran Sasso.

8 pages, 9 figures

References in corpus (4)

• The DAMA/LIBRA apparatus
• Annual modulation results from three-year exposure of ANAIS-112
• Characterization of SABRE crystal NaI-33 with direct underground counting
• High sensitivity characterization of an ultra-high purity NaI(Tl) crystal scintillator with the SABRE proof-of-principle detector

Cited by in corpus (7)

• Direct detection of dark matter: a critical review
• Simulation and background characterisation of the SABRE South experiment
• Towards a Robust Model-Independent Test of the DAMA/LIBRA Dark Matter Signal: ANAIS-112 Results with Six Years of Data
• First use of large area SiPM matrices coupled with NaI(Tl) scintillating crystal for low energy dark matter search
• A nonlinear multiphysics model for the design validation of the ASTAROTH copper-steel cryogenic chamber
• Background stability and annual modulation test using PICOLON ultra-pure NaI(Tl) detector
• ASTAROTH: A Novel Detector for Dark Matter Direct Detection Using Cryogenic SiPMs