European Physical Journal C: Particles and Fields (Sep 2020)

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

  • B. J. Park,
  • J. J. Choi,
  • J. S. Choe,
  • O. Gileva,
  • C. Ha,
  • A. Iltis,
  • E. J. Jeon,
  • D. Y. Kim,
  • K. W. Kim,
  • S. K. Kim,
  • Y. D. Kim,
  • Y. J. Ko,
  • C. H. Lee,
  • H. S. Lee,
  • I. S. Lee,
  • M. H. Lee,
  • S. H. Lee,
  • S. J. Ra,
  • J. K. Son,
  • K. A. Shin

DOI
https://doi.org/10.1140/epjc/s10052-020-8386-8
Journal volume & issue
Vol. 80, no. 9
pp. 1 – 13

Abstract

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Abstract 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) thallium-doped 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.