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Mother of Neutrino Detectors

Berkeley physicists build a new device to detect one of the universe’s most elusive particles.

May 31, 2024
by Glen Martin
BERKELEY LAB

Neutrinos are the Zeligs of subatomic particles, ghostly chameleons produced in vast quantities by a variety of nuclear and cosmic processes—colliding black holes, the fusion reactions at the heart of every star, uranium and plutonium fission in nuclear power plants. Nearly massless and thus extremely difficult to detect, neutrinos pass through anything and everything, including planets like ours, effortlessly.

That’s more than an astrophysical curiosity—it’s also a potential security marker here on planet Earth, as anomalous quantities of neutrinos can ID nuclear power plants making illicit weapons materials.

Today’s neutrino detectors are unwieldy apparatuses, massive tanks of liquid surrounded by phototubes. On those rare occasions when a meandering neutrino actually encounters one of the liquid medium’s atoms, the interaction—a subatomic-level blip—is recorded.

While these detectors work, there is much room for improvement. And Berkeley has just taken a giant step in that direction with Eos, a new device consisting of a large cylinder filled with water and an “organic scintillator” (a material that produces photons when hit by charged particles) coupled with an array of light detectors that are three times more sensitive than those commonly used in current physics research.

Eos is specifically designed to detect anomalous remote neutrino production—i.e., at fission power plants across the globe, over distances greater than 100 meters. While radioactivity can be shielded from detection, neutrinos can’t. If a fission plant is generating weapons-grade nuclear materials, the new detector should be able to suss it out.

Project lead Gabriel Orebi Gann, a Berkeley associate professor of physics and faculty scientist at Lawrence Berkeley National Laboratory, told Berkeley News that the Eos device was named for the goddess of the dawn because it signals “the dawn of a new era in neutrino detection technology.” And it’s just the beginning. “What we would ultimately like to build is a much bigger detector called Theia,” Gann said. “Theia is the Titan goddess of light and Eos’s mother.”

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