High sensitivity characterization of an ultra-high purity NaI(Tl) crystal scintillator with the SABRE proof-of-principle detector

Abstract

We present new results on the radiopurity of a 3.4-kg NaI(Tl) crystal scintillator operated in the SABRE proof-of-principle detector setup. The amount of potassium contamination, determined by the direct counting of radioactive ${}^{40}$K, is found to be $2.2\pm 1.5$ ppb, lowest ever achieved for NaI(Tl) crystals. With the active veto, the average background rate in the crystal in the 1-6 keV energy region-of-interest (ROI) is $1.20\pm 0.05$ counts/day/kg/keV, which is a breakthrough since the DAMA/LIBRA experiment. Our background model indicates that the rate is dominated by ${}^{210}$Pb and that about half of this contamination is located in the PTFE reflector. We discuss ongoing developments of the crystal manufacture aimed at the further reduction of the background, including data from purification by zone refining. A projected background rate lower than $\sim$0.2 counts/day/kg/keV in the ROI is within reach. These results represent a benchmark for the development of next-generation NaI(Tl) detector arrays for the direct detection of dark matter particles.

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Cited by in corpus (10)

• Review on dark matter searches
• Improving ANAIS-112 sensitivity to DAMA/LIBRA signal with machine learning techniques
• Simulation and background characterisation of the SABRE South experiment
• Performance of the SABRE detector module in a purely passive shielding
• COSINE-100 Full Dataset Challenges the Annual Modulation Signal of DAMA/LIBRA
• The SABRE South Technical Design Report Executive Summary
• The ASTAROTH project
• Production and suppression of delayed light in NaI
• First use of large area SiPM matrices coupled with NaI(Tl) scintillating crystal for low energy dark matter search
• ASTAROTH: A Novel Detector for Dark Matter Direct Detection Using Cryogenic SiPMs