The completion of the vast underground caverns for the Deep Underground Neutrino Experiment (DUNE) paves the way for groundbreaking neutrino research involving an international team of more than 1,400 scientists and engineers.

Excavation workers have completed construction of the future home of giant particle detectors for the International Deep Underground Neutrino Experiment. Three enormous caverns located a mile below the surface form the centerpiece of a new research facility covering an underground area the size of approximately eight football fields.

Hosted by the U.S. Department of Energy’s Fermi National Laboratory, DUNE scientists will study the behavior of mysterious particles known as neutrinos to solve some of the biggest questions about our universe. Why is our universe made of matter? How does an exploding star create a black hole? Are neutrinos associated with dark matter or other undetectable particles?

The role of neutrino detectors

The caverns have room for four large neutrino detectors, each the size of a seven-story building (see 2-minute animation below). The detectors will be filled with liquid argon and will capture the rare interaction of neutrinos with the transparent liquid.

Every second, trillions of neutrinos pass through our body without us even realizing it. With DUNE, scientists will look for neutrinos from exploding stars and study the behavior of a neutrino beam produced at Fermilab near Chicago, about 800 miles east of underground caverns. The beam created by the world’s most powerful neutrino source will travel directly through the earth and rocks from Fermilab to the DUNE detectors in South Dakota. The neutrino path does not require a tunnel.

Excavation and construction successes

“Completing excavation in these extensive caverns is a significant achievement for this project,” said US Project Director Chris Mossey. “Completion of this step prepares the detector installation project to begin later this year and brings us closer to realizing the vision of making this world-class underground facility a reality.”

Engineering, construction and excavation teams have been working 4,850 feet below the surface since 2021 at the Sanford Underground Research Center, home of the South Dakota portion of DUNE. Builders dismantled heavy mining equipment and moved it underground in pieces, using the existing mine. Underground, workers reassembled the equipment, and workers spent nearly two years blasting and removing the rock. Approximately 800,000 tons of rock were excavated and moved underground to a large section of old rock above ground, known as an open cut.

Next steps and safety notes

Workers will soon begin equipping the caves with the systems necessary for the installation of DUNE detectors and the daily operation of the research center. Later this year, the project team plans to begin installing the insulated steel structure that will house the first neutrino detector. The goal is to launch the first detector by the end of 2028.

The completion of the three large caves and all their connection points marks the end of the truly major excavations. The excavation contractor had an exemplary safety record, working more than one million accident-free hours. This is a major achievement in this heavy construction industry,” said Fermilab’s Michael Gemelli, who led the excavation of the caverns for Thyssen Mining. “The success of this phase of the project can be attributed to the safe and dedicated work of the excavators and the multidisciplinary expertise of the project engineers and support staff. What a remarkable achievement and milestone for this international project.”

DUNE scientists are eager to start building particle detectors. The DUNE collaboration, involving more than 1,400 scientists and engineers from more than 200 institutions in 36 countries, successfully tested the technology and assembly process of the first detector. Mass production of its components started. Testing of the technologies underlying both detectors continues at the European CERN laboratory using particle beams.