Reduction of the radioactivity in sodium iodide (NaI) powder by recrystallization method

Shin, K. A.; Gileva, Olga; Kim, Yeongduk; Lee, Hyun Su; Park, Hyangkyu

doi:10.1007/s10967-018-6006-y

Cited by 27 publications

(22 citation statements)

References 19 publications

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“…As part of an effort to upgrade the on-going COSINE-100 experiment to the next-phase COSINE-200 experiment, we have conducted a R&D aimed at low-background NaI(Tl) crystal growth. An initial chemical purification stage based on a recrystallization method demonstrated sufficient reduction of K and Pb in the powder [39]. Based on this, a mass production facility for the powder purification was assembled in our institute [40].…”

Section: (): V-volmentioning

confidence: 99%

Development of ultra-pure NaI(Tl) detectors for the COSINE-200 experiment

et al. 2020

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The annual modulation signal observed by the DAMA experiment is a long-standing question in the community of dark matter direct detection. This necessitates an independent verification of its existence using the same detection technique. The COSINE-100 experiment has been operating with 106 kg of low-background NaI(Tl) detectors providing interesting checks on the DAMA signal. However, due to higher backgrounds in the NaI(Tl) crystals used in COSINE-100 relative to those used for DAMA, it was difficult to reach final conclusions. Since the start of COSINE-100 data taking in 2016, we also have initiated a program to develop ultra-pure NaI(Tl) crystals for COSINE-200, the next phase of the experiment. The program includes efforts of raw powder purification, ultra-pure NaI(Tl) crystal growth, and detector assembly techniques. After extensive research and development of NaI(Tl) crystal growth, we have successfully grown a few small-size (0.61-0.78 kg) thalliumdoped crystals with high radio-purity. A high light yield has been achieved by improvements of our detector assembly technique. Here we report the ultra-pure NaI(Tl) detector developments at the Institute for Basic Science, Korea. The technique developed here will be applied to the production of NaI(Tl) detectors for the COSINE-200 experiment.

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Section: (): V-volmentioning

confidence: 99%

Development of ultra-pure NaI(Tl) detectors for the COSINE-200 experiment

et al. 2020

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“…The COSINE group showed the significant 40 K suppression in the RC method [11]. Potassium in the aqueous solution of sodium iodide forms a well soluble potassium iodide (KI) or potassium hydroxide (KOH).…”

Section: Re-crystallization Methodsmentioning

confidence: 99%

Development of highly radiopure NaI(Tl) scintillator for PICOLON dark matter search project

Fushimi,

Kanemitsu,

Hirata

et al. 2021

Preprint

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The highly radiopure NaI(Tl) was developed to search for particle candidates of dark matter. The optimized methods were combined to reduce various radioactive impurities. The 40 K was effectively reduced by the re-crystallization method. The progenies of the decay chains of uranium and thorium were reduced by appropriate resins. The concentration of natural potassium in NaI(Tl) crystal was reduced down to 20 ppb. Concentrations of alpha-ray emitters were successfully reduced by appropriate selection of resin. The present concentration of thorium series and 226 Ra were 1.2 ± 1.4 µBq/kg and 13 ± 4 µBq/kg, respectively. No significant excess in the concentration of 210 Pb was obtained, and the upper limit was 5.7 µBq/kg at 90% C. L. The achieved level of radiopurity of NaI(Tl) crystals makes construction of a dark matter detector possible.

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“…A decreasing rate of twopulse events is evident and an exponential fit with R(t) = A exp(−t/τ ) is overlaid. Because initial purification of NaI powder [31,32] and decomposition of impurities from the crystal growing process [15], amounts of 232 Th and 228 Ra can be in non-equilibrium depending on their chemical properties. A similar non-equilibrium status between 238 U and 226 Ra was previously observed in the NaI(Tl) crystal [15].…”

Section: Consistency Check Of 228 Ra Decaysmentioning

confidence: 99%

Identification of new isomers in $$^{228}$$Ac: impact on dark matter searches

et al. 2021

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We report the identification of metastable isomeric states of $$^{228}$$ 228 Ac at 6.28 keV, 6.67 keV and 20.19 keV, with lifetimes of an order of 100 ns. These states are produced by the $$\beta $$ β -decay of $$^{228}$$ 228 Ra, a component of the $$^{232}$$ 232 Th decay chain, with $$\beta $$ β Q-values of 39.52 keV, 39.13 keV and 25.61 keV, respectively. Due to the low Q-value of $$^{228}$$ 228 Ra as well as the relative abundance of $$^{232}$$ 232 Th and their progeny in low background experiments, these observations potentially impact the low-energy background modeling of dark matter search experiments.

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Reduction of the radioactivity in sodium iodide (NaI) powder by recrystallization method

Cited by 27 publications

References 19 publications

Development of ultra-pure NaI(Tl) detectors for the COSINE-200 experiment

Development of ultra-pure NaI(Tl) detectors for the COSINE-200 experiment

Development of highly radiopure NaI(Tl) scintillator for PICOLON dark matter search project

Identification of new isomers in $$^{228}$$Ac: impact on dark matter searches

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