PICOLON dark matter search similar to Development of highly redio-pure NaI(Tl) scintilltor similar to

The PICOLON project is developing a high purity NaI(Tl) crystal by optimizing the purification methods. The reduction method for K-40 was established and we got sufficiently pure NaI(Tl) crystal for K-40. On the other hand, the concentration of Pb-210 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.