 Dark matter forms a giant sea, enclosing the milky way. The earth and solar system like a small fish, swimming in it.  Dark Matter particle has a small probability hitting the atomic nuclei (<1time/100kg day ）， producing atomic recoil ， Direct detection of dark matter is to detect the Signals produced by this type of atomic recoil.

Phonon Electron Photon

 Semi-Conductor （ Ge ， Si ）  Electric current and heat  Low -T （ 0.02K ）、 high-cost ， hard to scale  Crystal （ NaI ， CsI ）  light  Hard to rule out background  Noble gas-liquid (Xe ， Ar ）  Light and electrons  Good to distinguish signals ， ton scale

 We are on the verge of discovery! Dark Matter Rush!

 Can detect both light and electron ：  light ： through PMT  electrons ： strong electric field+ gas phase  Large target ： large target has self-shielding effects  Large atomic mass  Cross section is proportional to the square of A  Can be purified easily  Is complementary to the semi-conductor tech

 10kg Xe  Gran Sasso

 Upgrade of XENON10  Lower background than XENON10 by 100 times ， background event ／ kg day kev  Can discriminate gamma and nucear recoil by 99.5%  Continuous running since jan 2011

 Started in 2009  Major Institutions  Shanghai Jiaotong University  Shanghai Inst. of applied physics  Shangdong University  Peking University  University of Michigan  University of Maryland

 JinPing Hydropower plant has four water-passage tunnels of 13m diameters, two traffic tunnels of 6m diamters. Length of the tunnel, 17km  Maximum depth 2400m ( wm).

Cooling Bus Shield Xe Storage