World’s largest neutrino experiment begins construction a mile underground in US

The Fermi National Accelerator Laboratory (FermiLab), European Organization for Nuclear Research (CERN), and the Sanford Underground Research Facility (SURF) have teamed up to build the Deep Underground Neutrino Experiment (DUNE) in South Dakota.

Located nearly a mile underground, the experiment uses giant cryostats to maintain liquid argon at extremely low temperatures. This setup would help study neutrinos, providing key insights into the aftermath of the Big Bang and broadening our fundamental understanding of the universe.

Neutrinos are subatomic particles that have no charge and almost no mass. Earning a ghostly reputation by avoiding gravity and nuclear forces, these abundant particles stream through us daily without leaving a single trace.

Since neutrinos are produced in stellar cores and can travel large distances, scientists can study them on Earth by building detectors. Observing neutrino interactions and how slight mass differences change their flavor can help explain why the universe has more matter than antimatter. It can also refine the Standard Model of Physics we use today.

A detector underground

DUNE is a world-leading experiment that is bringing more than 1,500 researchers together, who will be hosted at Fermilab. The cryostats being built at DUNE will hold liquid argon at -300 degrees Fahrenheit (-184 degrees Celsius).

Once the liquid argon detectors at DUNE are ready by 2030, the accelerator at Fermilab will be used to fire neutrinos at the detectors from 800 miles (1,300 km) away. Another detector located at Fermilab will also make measurements of the neutrinos before they travel and together form the Long Baseline Neutrino Facility.

A rendering of one of the cryostat modules that will house the liquid argon detector. Image credit: Fermilab/ Special Arrangement

Construction has now begun on the cryostats that will house approximately 17,000 tons of liquid argon. Each cryostat is 216 feet (65.8 m) long, 62 feet (18.9 m) wide, and 60 feet (18.3 m) high. A total of 2,600 steel beams will be used to build the two cryostats; the 6,200 tons of material being used to cast these beams is an in-kind contribution from CERN.

CERN’s major role outside Europe

CERN is leading the design, construction, logistics planning, and installation of DUNE’s cryostats. As a global leader in particle physics, the CERN team is sharing its expertise in building cryostats but has also built ProtoDUNE, the first of the two detector technologies that will be used in the experiment.

This is the first time CERN is making significant contributions to a project happening outside of Europe.

“Not only did we contribute our technical know-how, but also the project management capabilities of the organization,” said Lluís Miralles, Neutrino Platform principal project engineer at CERN in a press release shared with Interesting Engineering.

“CERN demonstrates here how, by design, we have in-house competencies to address requirements and challenges at all levels of the project.”

With the experiment being built underground, SURF has been assigned the responsibility of shaft operations and logistics to transport steel beams and other equipment to the site, 4,850 feet (1,478 m) below ground level.

As construction for the first cryostat has begun, SURF teams have also begun steel beam construction for the second cryostat, where assembly work is expected to begin next year.

The neutrino beam from Fermilab is expected to be sent to the underground detectors at DUNE by 2031.