Big device examines tiniest known particles
NOvA detector is world’s largest
Tom Klein
T. Klein
Cory Kolodji, a teacher at Chisholm, who provides tours at the detector during summers, shows the stacks of panels that are filled with mineral oil and electronics that are used to detect the neutrinos.

ASH RIVER – It takes an enormous device to examine one of tiniest building blocks of matter.

The $270-million neutrino detector completed this month at Ash River is the world’s largest free-standing PVC structure, consisting of 10,782 modules assembled by a team of University of Minnesota students over four years.

The device will allow scientists to learn more about subatomic particles known as neutrinos. Neutrinos are abundant in nature, but they rarely interact with other matter. Studying the particles could help unlock clues about the beginning of the universe.

Neutrinos come in three flavors — muon, electron and Tau. One of the goals of the NOvA (NUMI Off-Axis electron neutrino Appearance) experiment is to determine the order of neutrino masses, called mass hierarchy.

Located in a subterranean chamber that descends more than 50 feet below the rocky surface, the detector stretches nearly the length of a football field and is set at the end of a particle beam generated 500 miles away at the Department of Energy’s Fermi National Accelerator Laboratory in Batvaia, Ill. A smaller, 222-ton detector is located at the Fermilab site, near the particle beam’s origin.

The detector at the Ash River site will work like a high-definition camera in capturing the neutrinos’ interaction. Scientists expect only a tiny fraction of neutrinos will be detected at the site — as few as one or two a month.

But the information gleaned from those rare occurrences will be invaluable, according to Marvin Marshak, director of the laboratory and one of the people who played a key role in steering neutrino studies to Ash River and Soudan.

Professor Mark Messier of Indiana University said scientists know neutrinos have mass and that there are three kinds of neutrinos, but much is still unknown about the particles.

The project will help scientists learn more about neturinos and add to the worldwide effort seeking more information about the particles, he said.

At a July 24 ceremony celebrating the detector’s completion, Regina Rameka of Fermilab, one of the partners in this experiment, hailed the detector as cutting-edge science.

Rameka said Fermilab has created a division focused on neutrinos where “the flagship experiment is the NOvA experiment.”

Although the NOvA experiment is scheduled to run for at least six years, it could conceivably go well beyond that benchmark depending on the information it yields, Rameka noted.

“We’re going to be running our neutrino beam to northern Minnesota for a very long time,” she said. “Neutrinos are the future of Fermilab and the future is bright.”

U.S. Sen. Amy Klobuchar, D-Minn., was unable to attend the ceremony, but sent a videotaped message.

“The completion of this project truly is something to celebrate,” she said. “After all, the research being done there just might help us unlock new knowledge of neutrinos, the building blocks of our universe.”

She said her grandfather, who earned his living in the mines and saved money in a coffee can for his child’s college education, would marvel that the nation’s top physicists were now working underground at Ash River and Soudan on a major scientific initiative.

“That’s a lot of planning, a lot of imagination and a lot of money saved in coffee cans to support a lot of students’ and professors’ education,” Klobuchar said. “We should be so proud.”

Collaborative effort

The project is a collaborative effort by the University of Minnesota, the Department of Energy Office of Science and Fermi National Accelerator Lab.

DOE provided most of the funding for the project, including a $45 million cooperative agreement for research between the U.S. Department of Energy and the University of Minnesota. In addition, $40.1 million was provided through the American Recovery and Reinvestment Act.

Pepin Carolan from the U.S. Department of Energy said the result was a highly successful partnership, thanks to the efforts of many. But he singled out Marshak for his vision and dedication to this project.

“Marvin’s coordination and hard work every step of the way and his uncanny ability to bring the right people in at the right time really made all of this possible,” said Carolan.

The project also brought together almost 208 collaborators from seven countries and 38 institutions, and provides opportunities for university students in both science and engineering.

Dr. Brian Herman, vice president of research at the University of Minnesota, said the project provides great opportunities for university students. “The international work going on here will fundamentally push forward our basic understanding of the universe and the origin of life.”

The Ash River site was selected for the off-axis readings from the NUMI beam because it allows for a beam where the particles are of a specific energy, allowing scientists to more easily reject potential backgrounds.

In addition, scientists wanted to have the longest distance possible from Fermilab and Ash River to veer off the center of the beam. It’s also the last road crossing the beam line before entering Canada.

The construction of the detector and its building created 80 full-time construction jobs and put 47 full-time technicans to work assembling the detector. Bill Miller, lab supervisor, estimated that more than $5 million was spent in the three-years when the detector was built.

A crew of about six will remain to operate the detector. It will cost approximately $1.5 million per year to operate the detector, according to Miller, who estimated that 85 percent of the budget will be spent on salaries and electricity. Electricity alone accounts for about $500,000 of the annual costs.

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