‘Engineering marvel’: Neutrino experiment takes next step with completion of caverns

A ceremony on Aug. 15, 2024, marks the completed excavation of caverns for the Deep Underground Neutrino Experiment in the Long-Baseline Neutrino Facility, at the Sanford Underground Research Facility within the former Homestake Mine in Lead. (Joshua Haiar/South Dakota Searchlight)

LEAD — A former gold mine in the Black Hills is a step closer to being mined for answers to fundamental questions about the universe.

Dignitaries and scientists went 4,850 feet underground Thursday at South Dakota’s Sanford Underground Research Facility — formerly the Homestake Mine — to celebrate the completion of the excavation phase for one of the largest science experiments in the world.

“It is truly an engineering marvel,” said Lia Merminga.

She’s the director of the Fermi National Accelerator Laboratory in Batavia, Illinois, which is the other facility participating in the experiment.

Scientists and dignitaries cut a ribbon on Aug. 15, 2024, at the Sanford Underground Research Facility in Lead to celebrate the completed excavation of caverns for the Deep Underground Neutrino Experiment in the Long-Baseline Neutrino Facility.

Thursday’s ceremony celebrated the completed excavation of over 800,000 tons of rock to make space for the research. To do the work, construction crews dismantled heavy mining equipment piece by piece and transported it underground, and workers reassembled the machinery to blast and relocate rock.

The excavated rock was conveyed across a street in Lead and dumped into the Open Cut, a pit left over from the Homestake mining era that’s 1 mile wide and 1,250 feet deep.

The excavation resulted in three connected caverns. Two will house neutrino detectors each containing 17,000 tons of cooled, liquid argon, and the third will store other equipment. The two detector caverns are massive: 92 feet high, 65 feet wide and about one and a half football fields deep.

The project’s next phase will outfit the caverns with the technology needed to house the world’s largest neutrino detectors in what will be called the Long-Baseline Neutrino Facility. That will require the movement of 60 loads of material into the mine, six days a week, for approximately the next five years.

Neutrinos are subatomic particles that are sometimes compared to ghosts due to their ability to move through mass without any interaction, according to Sanford Underground Research Facility Science Director Jaret Heise.

“Neutrinos are complicated,” he said. “The strangest particle we’ve ever seen.”

Studying neutrinos could help scientists learn why matter exists, how black holes form, and if neutrinos are connected to dark matter or other undiscovered particles.

A Fermilab video explains the Deep Underground Neutrino Experiment.

The plan for the Deep Underground Neutrino Experiment is to shoot a beam of neutrinos 800 miles through the earth from Fermilab in Illinois to the detectors in South Dakota. That will allow scientists to study how neutrinos change as they travel long distances. The deep underground location shields the experiment from cosmic radiation.

The Homestake Mine was the largest and deepest gold mine in North America. It closed in 2001, and in the years that followed, then-Gov. Mike Rounds helped to shepherd the conversion of a portion of the mine into the Sanford Underground Research Facility, which has housed other experiments beyond the one celebrated Thursday. Rounds, now a U.S. senator, attended the ceremony.

“When you have this type of investment here, not just from the federal government, but from other nations around the world, it sends a message that this is bigger than just one state or community,” Rounds said.

The project is one of the largest international science collaborations ever attempted. The U.S. Department of Energy, which includes Fermilab, has estimated the total cost of the experiment to be more than $3 billion. In 2023, the project had $314 million of economic output in South Dakota and created 1,923 jobs in the state, according to the Department of Energy.

Thursday’s event highlighted the project’s global collaboration, which involves over 1,400 scientists from 35 countries.

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