Particle Hunter

Scientists are designing a massive underground detector to study some of the most elusive particles in the universe. These particles, called neutrinos, have no charge and almost no mass. There are three known types, each with different properties, but some researchers think a fourth may exist. They hope the Deep Underground Neutrino Experiment (DUNE) could help them find it.

Detecting neutrinos requires taking small, extremely accurate measurements of how particles interact. To ensure accuracy, physicists are currently building prototypes of DUNE in Switzerland. These test models consist of steel tanks filled with 800 tons of liquid argon (Ar), an inert element that won’t react with other substances and interfere with the experiment. By 2022, scientists will begin building four additional tanks, each 20 times larger than the prototypes. They’ll sit deep underground in South Dakota, shielded from cosmic rays—energetic particles from space that could distort neutrino detection.

Eventually, researchers will fire a beam of neutrinos at these underground tanks from the nearest available source: the Fermi National Accelerator Laboratory (Fermilab) in Illinois, 1,300 kilometers (808 miles) away. A small number of these neutrinos will strike the argon atoms. The collisions will produce tiny flashes of light and create new particles.

By studying these interactions, scientists will learn more about the nature of neutrinos and their role in the universe. “We’re hoping to make some major discoveries,” says Mark Thomson, a physicist at Cambridge University in England who is helping to lead the project.