Scientists are building tunnels under South Dakota for an experiment that may solve the mysteries of the universe.
The DUNE neutrino detectors will be located more than 1600 m underground
Nearly seven years ago, crews began hauling 800,000 tons of rock from a former gold mine near Lead, South Dakota.
The three resulting underground caverns are 500 meters long and almost tall enough to support a seven-story building.
Estimated to cost at least 3 billion dollars, the DUNE (Deep Underground Neutrino Experiment) project is led by Fermilab scientists of the US Department of Energy, writes news.yahoo.com.
Ultimately, each cavern will contain 17,500 tons of liquid argon to help physicists at Fermilab detect elusive particles known as neutrinos, also known as “ghost particles”.
Neutrinos are subatomic particles that surround you and pass right through you without being noticed. The sun creates them; supernovae produce them; even bananas produce neutrinos.
“If you hold your hand up, there are 10 billion neutrinos from the sun going through your hand,”
every second, physicist and DUNE spokesperson Mary Bishai told Business Insider.
Neutrinos are nicknamed ghost particles because they have no electrical charge and therefore rarely interact with anything they come into contact with.
This also makes them extremely difficult to study, but scientists still persist because neutrinos may hold the key to unlocking the secrets of the universe, from what happened right after the Big Bang to observing the birth of a black hole.
A neutrino beam between Illinois and South Dakota
Studying a particle that does not emit radiation and is lighter than an electron is difficult. “Neutrino interactions are almost like needles in a haystack,” Bishai stated.
And Fermilab scientists want to study neutrinos in unprecedented detail like never before with DUNE.
This is why DUNE will have the largest neutrino detectors of its kind ever built.
Once complete, the experiment is designed to go live with a series of particle accelerators at Fermilab outside Chicago, Illinois.
One of the caves where the detectors for the DUNE project will be located
The accelerators will launch an extremely powerful beam of neutrinos, which will first pass through a detector at Fermilab. The beam will then travel underground a distance of 800 miles to the detectors at South Dakota's Sanford Underground Research Facility.
Along the way, the neutrinos will do something rather strange. There are three types of neutrinos, and the particles can switch from one to another, a phenomenon known as oscillation. A scientist at Fermilab compared the phenomenon to a house cat that transforms into a jaguar and then a tiger before returning to its original form.
Tracking how neutrinos change across such great distances between Illinois and South Dakota will help scientists better understand these oscillations, giving them a more complete picture than Fermilab's current NOvA experiment, which it runs 500 miles between Illinois and Minnesota.
Doing all of this 1.5 km underground protects the delicate, oscillating particles from the energetic cosmic rays that hit the Earth's surface every second and could interfere with the data.
Solving the mysteries of the universe
Scientists hope to answer three main questions with DUNE: why is the universe made of matter and not antimatter, what happens when a star collapses, and if protons decay?
“Immediately after the Big Bang, matter and antimatter were created in almost equal amounts” Bishai said. But today, as far as scientists can tell, the universe is made up almost entirely of matter.
“Why did we end up with a matter universe and not an antimatter universe?”, she added.
The DUNE beam is designed to create both neutrinos and antineutrinos – the antimatter version. Observing the oscillations of each type could help scientists figure out what happened to all the antimatter.
The project is also ready for supernova physics, Bishai said.
In 1987, astronomers witnessed a brilliant supernova that exploded closer than any other in the past 400 years. With the detectors available at the time, they were only able to detect a few dozen neutrinos.
There's a 40 percent chance another nearby star will explode in the next decade, Bishai said, and Fermilab hopes at least one of its detectors in South Dakota will be operational in time.
A detector this large could capture thousands of neutrinos and provide insights into how both black holes and neutron stars form.
Finally, scientists have yet to observe protons decaying, but theory predicts that they should. Protons are small, positively charged particles that are part of the nucleus of an atom.
A test neutrino detector, ProtoDUNE, was created at CERN
The observation of proton decay would have implications for Albert Einstein's belief that a single theory could unify all forces in nature.
If protons decay, it would take about 10 billion, trillion, trillion years. But neutrino detectors can look for different signatures of proton decay, Bishai said. “We would have a chance to see them, if these grand unified theories are correct.”
An ambitious project
There are currently several neutrino projects around the world, including at the Japan Proton Accelerator Research Complex (J-PARC) and the European Organization for Nuclear Research (CERN).
What makes DUNE unique is its use of argon and the large distance between its near and far detectors.
The project has had some budget and schedule setbacks, Scientific American reported in 2022. It is supposed to have four argon detectors, but will start with two.
The first could be operational by the end of 2028, Bishai said, with the second detector following the following year. They will be in place in the event of a supernova explosion, but the beam portion won't be ready until 2031.
That said, Bishai considers the project to have already achieved one of its greatest achievements, a collaboration between about 1,400 people from 36 countries. “It's big science,” she said. “
