More than a century after gold miners were drawn to Lead, South Dakota, the town’s former Homestake mine is attracting scientists pursuing a different kind of discovery. Construction of the Deep Underground Neutrino Experiment, known as Dune, is set to begin inside caverns roughly a mile beneath the Black Hills.
The project will involve assembling four enormous detectors made from more than 4,000 tonnes of steel. Together, they will hold 70,000 tonnes of liquid argon cooled to about -200C. Building the detectors is expected to take nearly three years, followed by another year to fill them with argon.
Once operational, Dune will detect neutrinos, nearly massless particles that rarely interact with matter. Around a trillion pass through the human body every second without being noticed. The experiment will examine neutrinos from the Sun and distant stellar events, as well as particles sent in a powerful beam from Fermilab, near Chicago, through about 800 miles (1,300km) of Earth.
When a neutrino collides with an argon atom, it produces a flash of light and an electrical signal. By analysing these events, researchers hope to better understand the particles’ different masses and their ability to change between three varieties, a phenomenon known as oscillation.
The findings could address major questions in physics, including why the universe contains matter rather than equal amounts of matter and antimatter. Dune will search for small differences between neutrinos and antineutrinos that might help explain this imbalance. It will also investigate neutrinos produced by stellar explosions and the formation of black holes.
The site has a notable history in neutrino research. In the 1960s, physicist Ray Davis used a detector deep inside the mine to record neutrinos from the Sun for the first time. After the mine closed in 2001, it was converted into the Sanford Underground Research Facility, which now hosts Dune and other experiments, including Lux-Zeplin.
The US-led Dune project has international partners, with the UK contributing detector components, computing systems and the graphite target used to generate the Fermilab neutrino beam. Scientists describe the installation as a major engineering challenge, comparable to building a ship underground.
For Lead, the transformation represents a shift from extracting resources beneath the Earth to using the underground site to study the universe. Local officials and researchers say the facility is bringing new scientific activity, workers and opportunities to the community.
Sources: The Guardian Science.