PICO-LON Dark Matter Search

It is an important task to find an annual modulation of WIMPs signal for identifying dark matter signal. To search for annual modulation signal by means of inorganic scintillators, a large mass and a highly radiopure detector is needed. PICO-LON (Planar Inorganic Crystal Observatory for LOw background Neutr(al)inos) is a dark matter search project with multi-array NaI(Tl) scintillators. The test module of PICO-LON whose dimension is 15cm×15cm×0.1cm gives enough performance, energy resolution and low energy threshold, for dark matter search. The highly radiopure NaI(Tl) crystal is indispensable to start a large mass experiment. We have developed highly radiopure NaI(Tl) scintillator. The U and Th chain impurities were precisely measured by meand of pulse shape analysis for NaI(Tl) scintillators. The future plan of KamLAND-PICO dark matter search project is proposed.