PandaX is designed to build and operate a ton-scale liquid xenon experiment to detect the so far elusive dark matter in the Universe. The PandaX experiment uses a two-phase (liquid and gas) xenon position-sensitive time projection chamber detector. It is located at CJPL, which is one of the deepest underground labs in the world. The program has evolved through a series of staged detectors — PandaX-I (120 kg), PandaX-II (580 kg), and PandaX-4T (3.7 tonnes) — and continues toward the multi-ten-tonne PandaX-20T, reaching sensitivities down to $10^{-47} cm^{2}$ for spin-independent WIMP-nucleon interactions and beyond.
PandaX-II dark matter experiment
PandaX-II is a dark matter direct detection experiment equipped with a half-ton scale dual-phase time projection chamber (TPC). The PandaX-II experiment started in Oct 2014 with the detector installation at CJPL, followed by about one year of engineering runs and tests. The commissioning run started on Nov 22, 2015. After collecting 19 days of effective data, this run stopped due to a high level of Krypton background. Nevertheless, a factor-of-two improvement on the spin-independent (SI) WIMP-nucleon cross section limits was obtained using this data compared to the final result from PandaX-I using 80 days of data. After a Krypton distillation campaign, the experiment restarted data taking in March 2016. The first physics run lasted until the end of June and collected 80 days of effective data. Combining the commissioning run and the first physics run, PandaX-II obtained the most stringent upper limits on the SI WIMP-nucleon cross sections for WIMPs with masses between 5 and 1000 GeV. The PandaX-II experiment concluded operation in June 2019.
The research on the neutrinoless double-beta decay of ${}^{136}Xe$ continues in the PandaX-III project.