PandaX: Particle and Astrophysical Xenon Experiments

PandaX is an experimental program which employs a series of xenon detectors to search for elusive dark matter particles and to study the fundamental properties of neutrinos. PandaX was founded in 2009 by Prof. Xiangdong Ji, who also served as the first spokesperson of the collaboration until 2018. Up to now, the collaboration has constructed and operated three generation of experiments, PandaX-I, PandaX-II, and PandaX-4T, with active target masses of 120 kg, 580 kg, and 3.7 tonne, respectively. The collaboration is also preparing for the next generation multi-ten-tonne experiment, PandaX-xT, aimed to be an ultimate dark matter direct detection experiment and a leading project to test the Majorana nature of the neutrinos. This new generation of the experiment is also envisioned to be carried out in steps, with PandaX-20T (20-ton) commencing operation in 2027.

See a list of scientific publications here.

PandaX-20T schematic PandaX-20T collaboration

PandaX-20T

PandaX-20T is the new phase of PandaX after PandaX-4T. The liquid xenon will be housed in a titanium double-walled cryostat with an inner diameter of 2 m and a height of 3 m. The time projection chamber (TPC) field cage will enclose a sensitive volume of 17 tons of xenon nominally. The photodetector system consists of two phototube arrays positioned at the top and bottom of the TPC. The top array includes 616 Hamamatsu R12699 PMTs, each featuring 2" × 2" metal-channel-plate multi-anode structures. The bottom array consists of 433 3" Hamamatsu R11410 PMTs.

To suppress and tag gamma and neutron backgrounds, the titanium cryostat will be surrounded by liquid scintillator modules with a 10 cm thickness. The entire detector assembly will be located at the center of a 900 m³ stainless steel tank filled with ultrapure water. This tank will be instrumented with 8" photosensors to function as a water Cherenkov detector.

The installation and commissioning of PandaX-20T are expected to commence in 2027. The operation plan for PandaX-20T remains flexible, allowing for opportunities to implement moderate upgrades. The current cryostat design allows an approximate 20% increase in xenon volume. We may further upgrade the cryostat to achieve even lower background levels. Further upgrade will proceed once sufficient funding is secured together with technical readiness.

Read the executive summary

The PandaX program

PandaX-4T
With 6 tonnes of total xenon and a 4-tonne sensitive target, PandaX-4T improves the dark matter sensitivity by an order of magnitude compared with PandaX-II. It also searches for neutrinoless double-beta decay of $^{136}$Xe and other signals from new physics. The experiment was commissioned in 2021 and operated until 2026.
PandaX-II
PandaX-II
PandaX-II was a half-tonne scale dual-phase xenon TPC operated at CJPL between 2014 and 2019. In 2016 and 2017 it produced world-leading constraints on dark matter-nucleon interactions.
PandaX-I
PandaX-I
PandaX-I was the first phase of the program, a 120 kg liquid xenon dual-phase TPC operated at CJPL. It established the detector technology and produced competitive low-mass WIMP limits.
PandaX-III
PandaX-III
PandaX-III is an R&D effort to develop a high-pressure gaseous xenon TPC as a potential technology to search for the neutrinoless double-beta decay of $^{136}$Xe.