Recently, the DAMA/LIBRA collaboration confirmed observation of a modulated signal consistent with the DM hypothesis at a 13σ level. However, independent observation of the signal at another location and verification of its connection to the DM scattering off atoms are required. For that purpose, we created underground laboratory at the Kamioka mine and specialized laboratory for crystal growth in Japan where we successfully manufactured large highly radio-pure NaI(Tl) crystals.
The talk covers several related subjects: 1) a status of the underground clean-room facility for the DM search at the Kamioka mine; 2) details of construction and operation of the HPGe, radon (ion-pulse ionization chamber and NaI(Tl)), a Li-loaded liquid scintillator fast neutron and 6LiF/ZnS thermal neutron detectors; 3) description of the underground test setup used to measure the radio-purity level of the NaI(Tl) crytals; 4) methods of the NaI purification and crystal growth techniques used for manufacturing of radio-pure NaI(Tl) crystals; 5) selection of the radio-pure components and test results for the new 4-inch ultra-low background Hamamatsu photomultiplier with a metal body R13444X. Also, results of the radio-purity measurements for two latest NaI(Tl) crystals (ingot 71 and 73) and their comparison to the DAMA/LIBRA detectors will be presented.