Cavern excavation completed for international neutrino research

15 February 2024

Excavation has been completed on three large caverns that will house the massive particle detectors for the international Deep Underground Neutrino Experiment (DUNE).

Hosted by the US Department of Energy’s Fermi National Accelerator Laboratory (Fermilab), DUNE scientists will study the behaviour of particles known as neutrinos to find out more about the universe.

The caverns, which are 1,600m below the surface at the Sanford Underground Research Facility in South Dakota, will provide space for four large neutrino detectors – each one about the size of a seven-storey building. The detectors will be filled with liquid argon and record the rare interaction of neutrinos with the transparent liquid.

Photo: Matthew Kapust, Sanford Underground Research Facility

Trillions of neutrinos travel through our bodies each second. With DUNE, scientists will look for neutrinos from exploding stars and examine the behaviour of a beam of neutrinos produced at Fermilab, located nearly 1,300km east of Chicago. From there the beam will travel straight through earth and rock to the DUNE detectors in South Dakota. No tunnel is necessary for the neutrinos’ path.

“The completion of the excavation of these enormous caverns is a significant achievement for this project,” said US project director Chris Mossey. “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.”

Work to create the caverns began in 2021and nearly 800,000 tons of rock has been excavated.

Workers will soon begin to fit out the caverns with the systems needed for the installation of the DUNE detectors and the daily operations of the research facility. Later this year, the project team plans to begin the installation of the insulated steel structure that will hold the first neutrino detector. The goal is to have the first detector operational before the end of 2028.

“The completion of the three large caverns and all of the interconnecting drifts marks the end of a really big dig. The excavation contractor maintained an exemplary safety record working over a million hours without a lost-time accident. That’s a major achievement in this heavy construction industry,” said Fermilab’s Michael Gemelli, who managed the excavation of the caverns by Thyssen Mining. “The success of this phase of the project can be attributed to the safe, dedicated work of the excavation workers, the multi-disciplined backgrounds of the project engineers and support personnel.”

The DUNE collaboration, which includes more than 1,400 scientists and engineers from over 200 institutions in 36 countries, has successfully tested the technology and assembly process for the first detector. Mass production of its components has begun. Testing of the technologies underlying both detectors is under way using particle beams at the European laboratory CERN.