Fermilab Completes Excavation One Mile Beneath the Earth's Surface

In a former gold mine, more than 1,400 scientists and engineers representing 200 institutions, including the University of Mississippi, and 36 countries are building the world's largest neutrino detection facility. The goal is to better understand the mysterious "ghost particle," which is approximately 1,000 times smaller than an electron.

Ole Miss is among the institutions partnering on Fermilab's Deep Underground Neutrino Experiment, or DUNE. Gavin Davies, principal investigator for DUNE's Mississippi group, said the completion of the excavation is a significant step toward better understanding the physics and interactions of neutrinos.

"This is going to be a new dawn for neutrino physics," said Davies, an assistant professor of physics who has worked with Fermilab for more than 13 years on the NOvA Project. "The possibilities are endless in my mind for what we can do with a better understanding of neutrinos."

Although scientists don't know any practical application for neutrinos, they hope that the particle's behavior can help them understand complex questions about the universe such as: Why is there more matter than antimatter in the universe? How does an exploding star create a black hole? Are neutrinos connected to dark matter or other undiscovered particles?

"Our job is to understand them," Davies said. "We have no idea what the full extent of the applications will be, but we didn't know the application of the electron before we harnessed them for electricity."

Neutrinos, which are so small that scientists have not found a way to calculate their mass, are abundant across the universe, he said.

"We're in what is basically a neutrino shower every day," Davies said. "Fortunately, neutrinos pass right through us."

Each second, some 100 trillion neutrinos pass through a human body undetected – that's where the neutrino gets the name "ghost particle," he said.

The particles are also notorious for changing their type. Physicists recognize three varieties of neutrinos – muon, tau and electron – but neutrinos have been known to change their variety unexpectedly, he said.

"This is why we care about them: they change," Davies said. "Imagine I give you a pint of chocolate ice cream, and you get home and its strawberry. That's what these particles are doing."

The caverns, in Lead, South Dakota, are more than a mile beneath the Earth's surface and will host four neutrino detectors, each incredibly complex devices that are about the size of a seven-story building.

When the facility is complete, researchers can examine the behavior of neutrinos produced at Fermilab's particle accelerator near Chicago after they travel more than 800 miles through the earth to the DUNE facility in South Dakota, he said.

The project team hopes to have the first detector operational before the end of 2028.

"The completion of the excavation of these enormous caverns is a significant achievement for this project," said Chris Mossey, DUNE's U.S. project director. "Completing this step prepares the project for installation of the detectors starting later this year and brings us a step closer towards fulfilling the vision of making this world-class underground facility a reality."

This research is supported by the Department of Energy grant DE-SC0021616.