Abstract SABRE is a dark matter direct detection experiment based on NaI(Tl) scintillating crystals. The primary goal of the experiment is to test the dark matter interpretation of the DAMA/LIBRA annual modulation signal. To reach its purpose, SABRE will operate an array of ultra-low background NaI(Tl) crystals within an active veto, based on liquid scintillator. Finally two twin detectors will be used, one in the northern hemisphere at Laboratori Nazionali del Gran Sasso, Italy (LNGS) and the other, first of its kind, in the southern hemisphere, in the Stawell Underground Physic Laboratory (SUPL). The collaboration has successfully developed a NaI(Tl) crystal with the impressive potassium content of about 4 ppb, according to the mass spectroscopy measurements. A value that, if confirmed, would be about 3 times lower than the DAMA/LIBRA crystals one. The first phase of the SABRE experiment, called SABRE Proof of Principle (PoP), aims to prove the achieved radiopurity by direct measurement of crystals at LNGS. This work reports the status of the PoP setup and the recent progresses on the development of low radioactivity NaI(Tl) crystals.
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The SABRE experiment
The dark matter interpretation of the DAMA/LIBRA annual modulation signal represents a long-standing open question in astroparticle physics. The SABRE experiment aims to test such claim, bringing the same detection technique to an unprecedented sensitivity. Based on ultra-low background NaI(Tl) scintillating crystals like DAMA, SABRE features a liquid scintillator Veto system, surrounding the main target, and it will deploy twin detectors: one in the Northern hemisphere at Laboratori Nazionali del Gran Sasso (LNGS), Italy and the other in the Stawell Underground Physics Laboratory (SUPL), Australia, first laboratory of this kind in the Southern hemisphere. The first very-high-purity crystal produced by the collaboration was shipped to LNGS in 2019 for characterization. It features a potassium contamination, measured by mass spectroscopy, of the order of 4 ppb, about three times lower than DAMA/LIBRA crystals. The first phase of the SABRE experiment is a Proof-of-Principle (PoP) detector featuring one crystal and a liquid scintillator Veto, at LNGS. This contribution will present the results of the stand-alone characterization of the first SABRE high-purity crystal, as well as the status of the PoP detector, commissioned early in the summer of 2020.
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- NSF-PAR ID:
- 10333487
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- International Journal of Modern Physics A
- Volume:
- 37
- Issue:
- 07
- ISSN:
- 0217-751X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The SABRE experiment aims to detect the annual modulation of the dark matter interaction rate by means of ultra-high purity NaI(Tl) crystals. It focuses on the achievement of a very low background to carry out a model-independent and high sensitivity test of the long-standing DAMA result. SABRE has recently completed a Proof-of-Principle (PoP) phase at the Gran Sasso National Laboratory, devoted to assess the radiopurity of the crystals. The results on the radiopurity of a 3.4-kg NaI(Tl) crystal scintillator grown within the SABRE Collaboration and operated underground in the SABRE-PoP setup, will be reported and discussed. The amount of potassium content in the crystal, determined by direct counting of 40 K, is found to be < 4.7 ppb at 90% CL. The average background rate in the 1-6 keV energy region of interest (ROI) is 1.20 ± 0.05 counts/day/kg/keV, which is, for the first time, comparable with DAMA/LIBRA-phasel. Our background model indicates that this rate is dominated by 210 Pb, and that about half of this contamination is located in the PTFE reflector wrapped around the crystal. Ongoing developments aimed at a further reduction of radioactive contaminants in the crystal indicates that a background rate ≤ 0.3 counts/day/kg/keV in the ROI is within reach. This value represents a benchmark for the development of next-generation NaI(Tl) detector arrays for the direct detection of dark matter particles.more » « less
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Abstract The SABRE (Sodium Iodide with Active Background REjection) experiment will search for an annually modulating signal from dark matter using an array of ultra-pure NaI(Tl) detectors surrounded by an active scintillator veto to further reduce the background. The first phase of the experiment is the SABRE Proof of Principle (PoP), a single 5 kg crystal detector operated in a liquid scintillator filled vessel at Laboratori Nazionali del Gran Sasso (LNGS). The SABRE-PoP installation is underway with the goal of running in 2018 and performing the first in situ measurement of the crystal background, testing the veto efficiency, and validating the SABRE concept. The second phase of SABRE will be twin arrays of NaI(Tl) detectors operating at LNGS and at the Stawell Underground Physics Laboratory (SUPL) in Australia. By locating detectors in both hemispheres, SABRE will minimize seasonal systematic effects. This paper presents the status report of the SABRE activities as well as the results from the most recent Monte Carlo simulation and the expected sensitivity.more » « less
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The SABRE (Sodium-iodide with Active Background REjection) experiment is a new detector based on NaI(Tl) scintillating crystals for the dark matter detection through the annual modulation. With ultra-pure crystals and an active veto system, based on liquid scintillator surrounding the crystal array, SABRE will reach unprecedented low background and the highest sensitivity among the present NaI(Tl) experiments. Moreover SABRE will be the first dark matter search with twin detectors located in the North and South hemispheres, in Gran Sasso National Laboratories (LNGS), Italy, and Stawell Underground Laboratories (SUPL), Australia, respectively. The double location will help to quantify possible seasonal effects, and is a unique feature to identify a modulation of dark matter origins. SABRE is presently in the Proof-of-Principle (PoP) phase, with the goal to measure the crystal intrinsic and cosmogenic backgrounds of one 5 kg crystal and the active veto efficiency. We have performed a full geometry Monte Carlo simulation in order to evaluate the background contributions in the two distinct operation modes foreseen for the PoP: the potassium Measurement Mode (KMM) and the Dark Matter Measurement Mode (DMM), where the liquid scintillator detector is used in coincidence or anti-coincidence with the crystal, respectively. This paper presents the results of a detailed background simulation and the expected sensitivity for the SABRE full scale experiment.more » « less
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We present the characterization of a low background NaI(Tl) crystal for the SABRE North experiment. The crystal NaI-33, was studied in two different setups at Laboratori Nazionali del Gran Sasso, Italy. The Proof-of-Principle (PoP) detector was equipped with a liquid scintillator veto and collected data for about one month (90 kg \times × days). The PoP-dry setup consisted of NaI-33 in a purely passive shielding and collected data for almost one year (891 kg \times × days). The average background in the energy region of interest (1-6 keV) for dark matter search was 1.20 \pm ± 0.05 and 1.39 \pm ± 0.02 counts/day/kg/keV within the PoP and the PoP-dry setup, respectively. This result opens to a new shielding design for the physics phase of the SABRE North detector, that does not foresee the use of an organic liquid scintillator external veto, in compliance with the new safety and environmental requirements of Laboratori Nazionali del Gran Sasso.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1142/S0217751X22400164
