In a collaborative experiment known as Sudbury Neutrino Observation (SNO+), an international team of scientists has made a significant breakthrough in detecting neutrinos. They have detected subatomic particles, known as antineutrinos, using pure water.
Scientists have had trouble detecting neutrinos and antineutrinos because of their sparse interactions with other matter and because they cannot be shielded, which means they can pass through anything. Neutrinos and antineutrinos are tiny subatomic particles that are the most prevalent in the universe and are thought to be the fundamental building blocks of matter. Yet, that does not imply that they are radioactive or hazardous. Every second, over 100 trillion neutrinos silently traverse our bodies.
These characteristics, however, also make these elusive particles helpful for comprehending a variety of physical phenomena, like the creation of the universe and the investigation of far-off celestial objects.
While high-energy reactions like nuclear reactions in stars typically produce neutrinos. On the other hand, protons and other particles collide and release neutrinos as a byproduct, antineutrinos. Antineutrinos are usually produced artificially.
Joshua Klein, the Edmund J. and Louise W. Kahn Term Professor in the School of Arts & Sciences, said, “So, monitoring reactors by measuring their antineutrinos tells us whether they are on or off and perhaps even what nuclear fuel they are burning.”
Klein explains that a reactor in a foreign country could therefore be monitored to see if that country is switching from a power-generating reactor to one making weapons-grade material. Completing the assessment with water alone means an array of large but inexpensive reactors could be built to ensure that a country is adhering to its commitments in a nuclear weapons treaty; for example, it is a handle on ensuring atomic nonproliferation.
“Reactor antineutrinos are very low in energy, and thus a detector must be very clear from even trace amounts of radioactivity. In addition, the detector must be able to ‘trigger’ at a low enough threshold that the events can be detected.”
“For a reactor as far away as 240km, it’s particularly important to contain at least 1,000 tons of water. SNO+ satisfied all these criteria.”
Klein credits his former trainees Tanner Kaptanglu and Logan Lebanowski for spearheading this effort. While the idea for this measurement formed part of Kaptanglu’s doctoral thesis, Lebanowski, a former postdoctoral researcher, oversaw the operation.
“With our instrumentation group here, we designed and built all the data acquisition electronics and developed the detector ‘trigger’ system, which allowed SNO+ to have an energy threshold low enough to detect the reactor antineutrinos.”
- A. Allega et al. Evidence of Antineutrinos from Distant Reactors Using Pure Water at SNO+. Physical Review Letters. DOI: 10.1103/PhysRevLett.130.091801