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Massive caverns for DUNE neutrino project nearly excavated

Excavation crews dig out the north cavern of the Long-Base Neutrino Facility for the Deep Underground Neutrino Experiment.
Matthew Kapust
Sanford Underground Research Facility
Excavation crews dig out the north cavern of the Long-Baseline Neutrino Facility for the Deep Underground Neutrino Experiment.

Excavation of three underground caverns to study neutrinos in the Sanford Underground Research Facility in Lead is nearly complete.

Two caverns are already finished and officials expect the last one will get fully excavated by the end of January.

Fermilab is digging the caverns as part of the Long-Baseline Neutrino Facility, which will host the DUNE experiment to study neutrinos. Neutrinos are an incredibly small particle and very abundant. Trillions of neutrinos travel through us every second, without interacting with our bodies.

Illustration of the LBNF underground caverns.
Illustration of the LBNF underground caverns.

The lab removed 800,000 tons of rock to make room for large vats of liquid argon, which will detect neutrinos beamed from Illinois.

The earth acts as a filter for the lab – reducing background cosmic radiation, allowing scientists to better observe those neutrinos. That’s why it’s nearly 5,000 feet underground.

Two of the larger caverns are over four football fields long, 65 feet wide and over 90 feet tall.

Josh Willhite is the project manager to build the underground facility.

“It is the true definition of awesome,” Willhite said. “You cannot look at a photograph and understand the scale of these caverns. These are the largest caverns at this kind of depth anywhere in the world and it is just amazing to stand there and look up at a shelf that’s 60 feet above you and still thirty feet from the ceiling. It’s amazing.”

Excavation began in 2020.

Crews are already pouring concrete in the completed caverns. It will take a couple years to install the infrastructure necessary for the experiment, which is when they will also start installing the liquid argon detectors.

“The detectors are expected to take a couple of years each to install the cryostat the detectors go in. Then, another year or so to install the detector. Then, another year to fill them," Willhite said. "So, we’re talking about the end of this decade when they’d start taking science.”

That’s when Fermilab will send an intense beam of neutrinos toward the detectors to measure their properties. Scientists believe neutrinos are a big part in understanding the origin of matter.

Lee Strubinger is SDPB’s Rapid City-based news and political reporter. A former reporter for Fort Lupton Press (CO) and Colorado Public Radio, Lee holds a master’s in public affairs reporting from the University of Illinois-Springfield.