Researchers successfully detected antineutrinos traveling more than 240 kilometers (150 miles) from a nuclear power plant using a detector filled solely with ultrapure water. This achievement represents a pioneering advancement in particle detection, as it is the first time water alone captured these elusive particles from a distant reactor.
The experiment took place at the SNO+ laboratory located deep underground in Ontario, Canada, beneath over two kilometers of rock. This extensive rock cover acts as a natural shield against cosmic rays, enabling the facility to record exceptionally clear particle signals. The detection relied on observing the faint Cherenkov radiation produced when antineutrinos interact with protons in water, yielding charged particles moving faster than light does in that medium.
Antineutrinos, the antimatter counterparts to neutrinos, are emitted during nuclear beta decay processes inside reactors. They rarely interact with matter due to their near massless, uncharged nature, earning them the nickname “ghost particles.” The ability to detect reactor antineutrinos with just water introduces a simpler and more cost-effective approach compared to traditional detectors that require specialized liquid scintillators.
Currently, the SNO+ detector operates with a liquid scintillator to amplify light signals, but its initial calibration phase used ultrapure water. Data gathered over that period revealed the faint antineutrino-induced flashes, confirming the breakthrough. This method opens new possibilities for monitoring nuclear reactors and studying particle physics with reduced technical complexity.