The PICO-LON project aims at search for cold dark matter by means of highly radio-pure and large volume NaI(Tl) scintillator. The NaI powder was purified by chemical processing to remove lead isotopes and selecting a high purity graphite crucible. The concentrations of radioactive impurities of 226Ra and 228Th were effectively reduced to 58 ± 4 μ Bq/kg and 1.5 ± 1.9 μ Bq/kg, respectively. It should be remarked that the concentration of 210Pb, which is crucial for the sensitivity to dark matter, was reduced to 24 ± 2 μ Bq/kg. The total background rate at 10 keVee was as low as 8 keV-1kg-1day-1, which was sufficiently low to search for dark matter. Further purification of NaI(Tl) ingot and future prospect of PICO-LON project is discussed.
|Journal||Journal of Physics: Conference Series|
|Publication status||Published - 2016 Jun 9|
|Event||14th International Conference on Topics in Astroparticle and Underground Physics, TAUP 2015 - Torino, Italy|
Duration: 2015 Sept 7 → 2015 Sept 11