Geneva, 18 September 2018. The largest liquid-argon neutrino detector in the world has just recorded its first particle tracks, signaling the start of a new chapter in the story of the international Deep Underground Neutrino Experiment (DUNE).

DUNE’s scientific mission is dedicated to unlocking the mysteries of neutrinos, the most abundant (and most mysterious) matter particles in the universe. Neutrinos are all around us, but we know very little about them. Scientists on the DUNE collaboration think that neutrinos may help answer one of the most pressing questions in physics: why we live in a universe dominated by matter. In other words, why we are here at all.

The enormous ProtoDUNE detector – the size of a three-story house and the shape of a gigantic cube – was built at CERN1, the European Laboratory for Particle Physics, as the first of two prototypes for what will be a much, much larger detector for the DUNE project, hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory in the United States. When the first DUNE detector modules record data in 2026, they will each be 20 times larger than these prototypes.

The first ProtoDUNE detector took two years to build and eight weeks to fill with 800 tons of liquid argon, which needs to be kept at temperatures below -184 degrees Celsius (-300 degrees Fahrenheit). The detector records traces of particles in that argon, from both cosmic rays and a beam created at CERN’s accelerator complex. Now that the first tracks have been seen, scientists will operate the detector over the next several months to test the technology in depth.

“Only two years ago we completed the new building at CERN to house two large-scale prototype detectors that form the building blocks for DUNE. Now we have the first detector taking beautiful data, and the second detector, which uses a different approach to liquid-argon technology, will be online in a few months.”Marzio Nessi, head of the Neutrino Platform at CERN.

The technology of the first ProtoDUNE detector will be the same to be used for the first of the DUNE detector modules in the United States, which will be built a mile underground at the Sanford Underground Research Facility in South Dakota. More than 1,000 scientists and engineers from 32 countries spanning five continents – Africa, Asia, Europe, North America and South America – are working on the development, design and construction of the DUNE detectors. The groundbreaking ceremony for the caverns that will house the experiment was held in July of 2017.

Full version of the press release by CERN, 18 September 2018

View of the interior of the ProtoDUNE experiment © CERN