Search for cosmic dark matter by means of ultra high purity NaI(Tl) scintillator

TL;DR

This paper discusses the development and application of ultra high purity NaI(Tl) scintillators with extremely low radioactive impurities for detecting dark matter signals.

Contribution

It reports the development of high purity NaI(Tl) crystals with significantly reduced radioactive impurities for dark matter searches.

Findings

Achieved impurity levels: <4 ppb K, 0.3 ppt Th, 58 μBq/kg Ra, 30 μBq/kg Pb.

Designed large volume NaI(Tl) detectors for dark matter detection.

Discussed future prospects for large-scale dark matter search using these detectors.

Abstract

The dark matter search project by means of ultra high purity NaI(Tl) scintillator is now underdevelopment. An array of large volume NaI(Tl) detectors whose volume is 12.7 cm$\phi\times$12.7 cm is applied to search for dark matter signal. To remove radioactive impurities in NaI(Tl) crystal is one of the most important task to find small number of dark matter signals. We have developed high purity NaI(Tl) crystal which contains small amounts of radioactive impurities, $<4$ ppb of $^{nat}$K, 0.3 ppt of Th chain, 58 $\mu$Bq/kg of $^{226}$Ra and 30 $\mu$Bq/kg of $^{210}$Pb. Future prospects to search for dark matter by means of a large volume and high purity NaI(Tl) scintillator is discussed.