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PICOLON (Pure Inorganic Crystal Observatory for LOw-energy Neutr(al)ino) aims to search for cosmic dark matter by high purity NaI(Tl) scintillator. We developed extremely pure NaI(Tl) crystal by hybrid purification method. The recent result of 210Pb in our NaI(Tl) is less than 5.7 μBq/kg. We will report the test experiment in the low-background measurement at Kamioka Underground Laboratory. The sensitivity for annual modulating signals and finding dark matter particles will be discussed.

The PICOLON project is developing a high purity NaI(Tl) crystal by optimizing the purification methods. The reduction method for 40K was established and we got sufficiently pure NaI(Tl) crystal for 40K. On the other hand, the concentration of 210Pb is still higher than our goal. The investigation is now in progress to fix the origin of the contamination. The construction of the second phase detector system of PICOLON detector will be started in 2020 spring. The total mass of the second phase is about 54 kg. The background level by the test measurement using a single module is reported.

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