Ground-breaking 'antineutrino' detector requires pure water only

Also, they can be used in the real world to watch over nuclear reactors and possibly learn about secret nuclear activities.

While neutrinos are produced by high-energy reactions like nuclear reactions in stars, antineutrinos are usually produced artificially by nuclear reactors. By measuring antineutrinos from reactors, scientists can tell if a reactor is on or off and maybe even what kind of nuclear fuel it is burning.

This method could help monitor a reactor in a foreign country and determine if the country is switching from a power-generating reactor to one making weapons-grade material.

However, reactor antineutrinos are low in energy, making it difficult to detect them. The detector must be clean from any trace amounts of radioactivity and have a low enough threshold to detect the events. Additionally, the reactor must contain at least 1,000 tons of water to monitor a reactor as far away as 149.13 miles (240 kilometers).

Klein says his former students Tanner Kaptanglu and Logan Lebanowski led the way. Kaptanglu's doctoral thesis was part of the idea for the measurement, and Lebanowski, who used to be a postdoctoral researcher, was in charge of the whole thing. The instrumentation group designed and built all the data acquisition electronics and developed the detector's trigger system, allowing SNO+ to have an energy threshold low enough to detect the reactor antineutrinos.

This breakthrough in detecting antineutrinos with just water could lead to large and inexpensive detectors, ensuring a country is adhering to its commitments in a nuclear weapons treaty and providing a handle on ensuring nuclear nonproliferation. This discovery also opens new ways to study and use these elusive particles in the real world.

You can read the study for yourself in the journal Physical Review Letters.

Study abstract:

"The SNO+ Collaboration reports the first evidence of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240 km away in Ontario, Canada. This analysis uses events with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods are used to distinguish reactor antineutrinos from background events in 190 days of data and yield consistent evidence for antineutrinos with a combined significance of 3.5σ."