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　 0.005 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 (6000-7000 wm).

Cooling Bus

Shield

Xe Storage