Why Fermilab could blast up campus, shake up Batavia neighbors

At least 300 billion neutrinos passed through one of your fingernails in the time it took you to read this sentence.

And while they passed through you, your office door, the building's walls and Earth's atmosphere, these ubiquitous building blocks of the universe may have changed their nature - and changed it back again.

Scientists from around the world hope to learn more about these particles in a proposed experiment that would be headquartered at Fermi National Accelerator Laboratory in Batavia.

And that would mean, once again, construction of big objects to study tiny ones.

The Deep Underground Neutrino Experiment, or DUNE, would shoot neutrinos out to a detector 800 miles away, in a former gold mine in South Dakota. That's 300 miles farther, and 100 percent deeper, than two current Fermilab-based experiments do, when they send neutrinos to a detector in Minnesota.

Why do it?

Why build a new experiment? The greater distance will give the neutrinos more opportunity to transform from type (called a "flavor") to type, said Steve Brice, deputy head of Fermilab's neutrino division.

There are three flavors: muon neutrinos, electron neutrinos and tau neutrinos. There's also newer, better technology to detect neutrinos than there was 15 years ago, when the current experiments were started. And going farther results in a wider range of energy, Brice said.

Neutrinos are elusive little things, most of which are sent our way by the sun. They don't interact much with other subatomic particles, so by themselves they wouldn't seem to be a big deal. But because they are the most abundant particle there is, scientists believe they have had a strong effect on how the universe evolved and continues to change.

Measuring the differences among the three types could help answer a pesky question: Why there is more matter than antimatter in the universe, seemingly violating the principle of symmetry?

Matter and antimatter should annihilate each other, leaving nothing but light, said Cambridge University Professor Mark Thomson, co-spokesman for the experiment. That, he said, "would make for a dull universe."

"It's about understanding how our universe works," Brice said.

Both neutrinos and anti-neutrinos will be sent, at different times.

The best chance to document neutrinos is when they hit liquefied argon gas in a detector, according to Brice and Thomson.

"Every once in a while one will hit an argon nucleus," Brice said, causing a spray of particles whose energy can be recorded. In South Dakota, there will be four detectors - each 60 meters long, 15 meters tall and 15 meters wide, filled with argon gas chilled to -303 degrees Fahrenheit.

The new experiment will send muon-type neutrinos out and expect them to change into electron-type neutrinos by the time they hit the argon in South Dakota 4 milliseconds later.

As with other pure science experiments, those working on DUNE aren't seeking a practical application for what they will learn. That doesn't mean learning more about neutrinos won't prove useful.

"Whenever you are pushing the boundaries of science or technological development you can see all kinds of interesting spinoffs," Brice said.

There have been proposals, for example, to use neutrino detectors to monitor nuclear-power-generation plants to determine if they are being used instead to make weapons. Neutrinos resulting from uranium fission for electrical power production have different characteristics than those from plutonium fission. Plutonium is used in nuclear weapons.

Why Fermilab?

"Fermilab is the place where you have the most powerful beams," Thomson said.

The chance of a neutrino interacting with an argon molecule is something like 1 in 1 trillion, he said; Fermilab's ability to send the most neutrinos out improves the odds, like "buying lots of lottery tickets," Thomson said.

Fermilab also has the expertise on hand to build underground halls and scientific equipment, he said.

The DUNE experiment would be among more than 20 Fermilab participates in, 15 of which are largely based at Fermilab, according to Fermilab spokesman Andre Salles.

Hard-hat science

Conducting the experiment would require building the Long-Baseline Neutrino Facility on the west side of the 6,800-acre laboratory campus. It would have four buildings, a tunnel, two underground chambers and a five-story hill.

The neutrinos would be supplied by the existing Main Injector proton accelerator. It will shoot protons up and then down the 58-foot-tall hill. They will smash into a piece of graphite, shaking loose the neutrinos and other particles as they travel a 680-foot tunnel to an absorber hall 94 feet below ground.

The neutrinos will travel on to a detector 183 feet underground on Fermilab property, then to detectors in a cavern 4,850 feet below ground at the Sanford Underground Research Facility in Lead, South Dakota.

More information about the proposed neutrino facility is available at lbnf.fnal.gov, and about DUNE at dunescience.org.

Public comment on the construction, including its environmental impact, is being accepted in writing through Friday, July 10.

The U.S. Department of Energy will then prepare a final version of the environmental assessment. If nothing significant is found, construction can proceed.

It would start at the South Dakota sites next year, and at Fermilab in 2018 or 2019. The experiment would likely begin running in 2025, Salles said.

The environmental assessment takes into account the construction's effect on the land, water, traffic, air quality, waste disposal and more. It estimates that to build the underground portions, there will be blasting four times a day for several months, blasting that could be felt by residents west of Fermilab.

That is, if an international agreement can be brokered to help pay for the experiment. Big science costs big money. In 2012, a former Fermilab director estimated the cost at $1.2 billion to $1.5 billion.

Salles and Brice would not say if those figures still apply, as negotiations are underway with other countries.

"This is a big undertaking for U.S. particle physics," Thomson said.

"I like thinking of this as the Large Hadron Collider of neutrinos."