The US has begun lowering 10 million pounds of steel nearly a mile underground to build the Deep Underground Neutrino Experiment (DUNE), widely regarded as one of the world’s most ambitious particle physics experiments.

The Fermi National Accelerator Laboratory (Fermilab), the premier US national lab for high-energy particle physics announced the start of the underground detector assembly for the massive neutrino project in South Dakota on May 7. It is carried out along with the Sanford Underground Research Facility and CERN.

Transported deep underground, the steel beams will be used for the construction of massive detector modules that will help Fermilab engineers to study neutrinos, some of the most common and least understood particles in the universe.

Norbert Holtkamp, Fermilab director, highlighted the importance of the advance. “Today represents the start of a pivotal phase for DUNE, the development of the far detector structures in South Dakota,” he elaborated.

A new construction phase

DUNE brings together scientists and engineers from over 35 countries around the globe. Once fully operational, it will send the world’s most intense neutrino beam roughly 800 miles from Fermilab in Illinois to detectors buried deep beneath the ground at SURF in South Dakota.

For the project, the European Organization for Nuclear Research (CERN) provided personnel, expertise, and 10 million lbs of steel for the underground detectors. It is the organization’s first infrastructure investment outside Europe.

The steel beams will be used to build the cryostats. These are massive insulated containers made to hold liquid argon cooled to -300 degrees Fahrenheit. These detectors will capture neutrino interactions with unprecedented precision.

Each of the first two detector modules will be massive. In practice, this translates to roughly 216 feet long, 62 feet wide, and 60 feet high, which is equal to the size of a five-story building. Once completed, each cryostat will contain approximately 17,000 tons of liquid argon, nearly a mile underground.

Going underground

Mark Thomson, CERN director general, revealed that CERN is supplying prototype detectors and giant cryostats for DUNE, while in parallel, US labs are providing superconducting magnets for the High-Luminosity Large Hadron Collider. “This important milestone for DUNE is a testament to the strong scientific partnership between CERN and the US,” Thomson concluded in a press release.

The DUNE experiment is the largest scientific project currently backed by the US Department of Energy (DOE) Office of Science. It is, additionally, one of the most important neutrino experiments ever attempted.

Neutrinos are highly difficult to study because they rarely interact with matter. Billions pass through the human body every second unnoticed. According to Fermilab, the project could help answer some of the biggest physics mysteries, including why matter dominates over antimatter in the universe and how the universe evolved after the Big Bang.

The team also believes that the research could influence fields, including national security, communications, and medical imaging. The project brings together more than 1,500 scientists from institutions worldwide. With underground installation now underway, Fermilab’s next major target is delivering the first neutrino beam to DUNE by 2031.