Growth of Ultra-high Purity NaI(Tl) Crystal for Dark Matter Searches

Abstract

The annual modulation of scintillation event rate observed by the DAMA/LIBRA experiment has been a long-standing controversy in the quest of the direct detection of dark matter. The effort to definitively confirm or refute the annual modulation has turned out to be challenging due to the lack of NaI(Tl) crystals with high enough radio-purity. Most recently, we successfully grew a 6-kg ingot free from contamination during growth, from which a 3.4-kg crystal scintillator was made. The ${}^{39}$K concentration in the final crystal is estimated to be 4.3$\pm$0.2~ppb, unprecedented for NaI(Tl) crystals. The ${}^{210}$Pb activity is estimated to be 0.34$\pm$0.04~mBq/kg via $\alpha$ counting of ${}^{210}$Po, among the lowest of currently-running NaI-based dark matter experiments except DAMA/LIBRA. More importantly, the techniques and protocols we have developed will further contribute to the growth of higher purity NaI(Tl) crystals for dark matter searches.

References in corpus (3)

• The DAMA/LIBRA apparatus
• Low-Mass Dark Matter Search with CDMSlite
• Cosmogenic production of tritium in dark matter detectors

Cited by in corpus (16)

• Strong constraints from COSINE-100 on the DAMA dark matter results using the same sodium iodide target
• Exploring coherent elastic neutrino-nucleus scattering using reactor electron antineutrinos in the NEON experiment
• Development of ultra-pure NaI(Tl) detectors for the COSINE-200 experiment
• Direct Detection of Dark Matter -- APPEC Committee Report
• 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
• Annual modulations from secular variations: relaxing DAMA?
• Scintillation characteristics of a NaI(Tl) crystal at low-temperature with silicon photomultiplier
• Performance of an ultra-pure NaI(Tl) detector produced by an indigenously-developed purification method and crystal growth for the COSINE-200 experiment
• Study on NaI(Tl) crystal at -35 C for dark matter detection
• Sensitivities for coherent elastic scattering of solar and supernova neutrinos with future NaI(Tl) dark matter search detectors of COSINE-200/1T
• Inelastic Dark Matter and the SABRE Experiment
• Zone refining of ultra-high purity sodium iodide for low-background detectors
• The SABRE South Technical Design Report Executive Summary
• Testing the Gallium Anomaly
• The role of small scale experiments in the direct detection of dark matter