XENONnT reduces radon background to below the neutrino level

In the search for dark matter, the XENONnT experiment at LNGS stands out as one of the world’s most sensitive detectors in the field with an extremely low background level. XENONnT has achieved a major technological breakthrough: a significant reduction of radioactive radon.

The XENONnT radon removal system

The core of this innovation is a cryogenic distillation system that purifies the liquid xenon inside the detector. The new system has reduced radon-induced radioactivity to an extraordinarily low level: a billion times lower than the natural radioactivity of the human body and a factor of four lower than the previous record level in XENONnT. This achievement is crucial for detecting the extremely faint signals in xenon-based detectors from rare particle interactions that could reveal the nature of dark matter.

The unique radon distillation column continuously purifies the xenon, lowering the radon concentration down to just 430 radon atoms per tonne of liquid xenon, making their background contribution as low as that from solar neutrinos. This sets a new benchmark for purity in xenon-based detectors and enhances sensitivity to rare particle interactions.

This work has been published in Physical Review X and was featured in an accompanying Physics Synopsis article:

Physics Synopsis Article: Dark-Matter Sensitivity Improved with a Xenon Still
LNGS press release
Original article:
Radon Removal in XENONnT down to the Solar Neutrino Level
E. Aprile et al. (XENON Collaboration)
Phys. Rev. X 15, 031079, arXiv:2502.04209.