The PandaX experiment of China is located in a deep underground laboratory, shielded by 2,400 meters of low radioactive rocks to provide protection for PandaX against cosmic muons. It began operation in March but has no results yet, so they published a technical design report to show the Chinese government they are doing something.

Established in 2009, the Particle and Astrophysical Xenon (PandaX) collaboration was established in 2009 and is geared toward both direct dark matter detection and Xe-136 neutrinoless double beta decay search. The experiment employs Xenon dual-phase technology to capture both the primary scintillation and the ionization from proportional scintillation, similar to the XENON and LUX experiments. Currently, the experiment is running at a target mass about 120kg, similar to that of XENON100 but it could be upgraded to half-ton scale mass.

Muon flux in the China Jinping underground laboratory (CJPL) was measured to be the lowest one among all similar experiments. A passive shield consists of about 100 tons of lead and copper and was constructed to attenuate the neutrons and gammas from environmental materials, such as cavern wall rocks and concrete. Given those efforts, the PandaX detector is running within a low background environment.

A reliable cryogenic and gas-handling system for PandaX was built and operated successfully in the past several years. The facility was moved into CJPL in August, 2012. The Xenon dual-phase technology was verified in the two commissioning runs in 2013 and early 2014, in which the key parameters of the experiment, such as the light yield, were measured. The experiment started to take science data from late March, 2014.

The first result of PandaX is expected to be released late this year. 

SCIENCE CHINA Physics, Mechanics&Astronomy, 2014, 57(8): 1476-1494.