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

Abstract

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 226Ra were $1.2\pm 1.4$ $\mu$Bq/kg and $13\pm 4$ $\mu$Bq/kg, respectively. No significant excess in the concentration of ${}^{210}$Pb was obtained, and the upper limit was 5.7 $\mu$Bq/kg at 90% C. L. The achieved level of radiopurity of NaI(Tl) crystals makes construction of a dark matter detector possible.

11 pages, 6 figures, accepted to Progress of Theoretical and Experimental Physics

References in corpus (3)

• The DAMA/LIBRA apparatus
• Constraining the Spin-Dependent WIMP-Nucleon Cross Sections with XENON1T
• Characterization of SABRE crystal NaI-33 with direct underground counting

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
• Direct Detection of Dark Matter -- APPEC Committee Report
• Scintillation characteristics of a NaI(Tl) crystal at low-temperature with silicon photomultiplier
• Improving ANAIS-112 sensitivity to DAMA/LIBRA signal with machine learning techniques
• Performance of an ultra-pure NaI(Tl) detector produced by an indigenously-developed purification method and crystal growth for the COSINE-200 experiment
• Sensitivities for coherent elastic scattering of solar and supernova neutrinos with future NaI(Tl) dark matter search detectors of COSINE-200/1T
• Upgrading the COSINE-100 Experiment for Enhanced Sensitivity to Low-Mass Dark Matter Detection
• Study on NaI(Tl) crystal at -35 C for dark matter detection
• COSINE-100 Full Dataset Challenges the Annual Modulation Signal of DAMA/LIBRA
• Cosmogenic activation of sodium iodide
• The role of small scale experiments in the direct detection of dark matter
• The ASTAROTH project
• Towards a Robust Model-Independent Test of the DAMA/LIBRA Dark Matter Signal: ANAIS-112 Results with Six Years of Data
• Development of a method to measure trace level of uranium and thorium in scintillation films
• Background stability and annual modulation test using PICOLON ultra-pure NaI(Tl) detector