The XENON Experiment
Installation of the XENONnT top PMT array into its Cu holding structure before placement into the TPC
The XENON dark matter experiment is installed underground at the Laboratory Nazionali del Gran Sasso of INFN, Italy.
For XENON1T, more than 3 tons of liquid xenon target were operated as a dual phase (liquid/gas) time projection chamber to search for interactions of dark matter particles. An interaction in the target generates scintillation light which is recorded as a prompt signal by two arrays of photomultiplier tubes (PMTs) at the top and bottom of the chamber. In addition, each interaction liberates electrons, which are drifted by an electric field to the liquid-gas interface. There, a strong electric field extracts the electrons and generates proportional scintillation which is recorded by the same photomultiplier arrays as a delayed signal. The ratio of the two signals allows to discriminate electronic recoils, which are the dominant background, from nuclear recoils, which are expected from Dark Matter interactions.
With this technique and the ultrapure liquid, XENON1T in 2018 was setting the world´s most sensitive limits on WIMP Dark Matter.
The next stage in this endeavour is XENONnT with more than 8 tons of Xenon, aiming at increasing the sensitivity by another factor 20.