SNO+ Detects Reactor Antineutrinos 240 Kilometers Away Using Water Alone
Updated
Updated · ScienceAlert · Jul 1
SNO+ Detects Reactor Antineutrinos 240 Kilometers Away Using Water Alone
2 articles · Updated · ScienceAlert · Jul 1
Summary
A 2018 SNO+ calibration run found the first reactor antineutrino detected with ultrapure water alone, tracing the particle to a nuclear reactor more than 240 kilometers away.
190 days of data revealed inverse beta decay signatures, including a 2.2-megaelectronvolt neutron-capture flash; the candidate event reached 3-sigma confidence, or 99.7% probability.
The result mattered because water detectors usually struggle below 3 megaelectronvolts, but water-filled SNO+ detected down to 1.4 megaelectronvolts with roughly 50% efficiency at 2.2 megaelectronvolts.
Buried under more than 2 kilometers of rock in Ontario, the detector used shielding from cosmic rays to isolate the faint signal, suggesting plain water could support cheaper, safer remote reactor monitoring.
SNO+, now operating with liquid scintillator in its 780-tonne tank, has since produced precision neutrino measurements and is still searching for a rare decay that could show whether neutrinos and antineutrinos are the same particle.