World’s most sensitive dark matter detector cuts radon by billionfold

The XENON Collaboration, operating one of the world’s most sensitive dark matter detectors at Italy’s Gran Sasso Laboratory, has achieved a major breakthrough by drastically reducing background radioactivity caused by radon gas inside their detector. Using an advanced cryogenic distillation system, the team lowered radon concentrations to about 430 atoms per metric ton of liquid xenon—approximately a billion times less than natural radiation levels found in the human body. This reduction minimizes false signals that could mimic dark matter interactions, pushing the experiment into a sensitivity regime limited only by neutrino background, which cannot be shielded against. The detector contains 8.5 metric tons of liquid xenon cooled to minus 95 degrees Celsius and is located deep underground to shield it from cosmic radiation. Radon, a decay product of ancient elements, has been a persistent source of interference due to its radioactive decay producing light flashes in the detector. The new purification technology represents a significant step toward directly detecting dark matter, which is believed to