NOvA Far Detector

Summary

Fermi National Accelerator Laboratory (Fermilab), the premier research facility in the United States for the study of sub-atomic particles, built a large physics detector in northern Minnesota to intercept and detect neutrons produced approximately 550 miles away at Fermilab in Batavia, Illinois, approximately 40 miles west of Chicago. Neutrinos can change from one type to another, and understanding the details of how they change is an important goal of the worldwide physics community. The combination of the neutrino beam at Fermilab and the new detector site in Minnesota provides a unique opportunity to study neutrinos more precisely that at any other existing facility.

Burns & McDonnell was retained by Fermilab to design the neutrino detector facility. The facility design package was a multidiscipline effort. Of particular interest is the structural design, which was complicated by the subterranean nature of the neutrino detector, combined with the cosmic shielding requirements of the detector. The detector enclosure must be fitted with additional material to shield the detector components from cosmic rays, which have similar properties to neutrinos and could cause confusion during the study period. The shielding design incorporates 10 feet of granite rock overburden along the perimeter of the detector enclosure and a combination of a normal weight concrete and barite enhanced concrete or barite aggregate for the enclosure roof.

The project was recognized in February 2013 with an Engineering Excellence Honor Award from the American Council of Engineering Companies of Illinois.

Services

• Architecture
• Engineering design
• Building information modeling (BIM)
• 3-D modeling

Background

The NOvA Far Detector Building in northern Minnesota houses a high-tech catcher's mitt for subatomic particles that have traveled 500 miles in less than three-millionths of a second.

In an experiment designed to help physicists understand the origins of the universe, a neutrino beam fired from Enrico Fermi National Accelerator Laboratory in Batavia, Illinois, will cross beneath Wisconsin and the nose of Lake Superior, traveling 6 miles below the Earth's surface before passing through the site along the Ash River. The few particles that hit the 14,000-ton neutrino detector housed there will give up their cosmic secrets before crossing into Canada.

Building information modeling (BIM) technology was employed to identify logistical and scheduling issues, demonstrate how building components would fit together, and create a real-time communication plan for stakeholders. An unusual application led to the development of 3-D laser scanning, which helped minimize layout time for excavation.

Access to the remote and environmentally sensitive site was achieved by upgrading an existing logging road to a hard all-weather surface while minimizing impact on adjacent groundwater, wetlands and historic sites. The remote location and limited water supply required installation of a high-pressure, water-mist fire suppression system similar to those found on cruise ships, only the second major installation of this type in America.

Burns & McDonnell coordinated with the National Park Service to "soften" external design features and adhere to a "dark sky" initiative, consistent with the site's wilderness setting.

Features

The massive, 350-foot-long concrete structure was buried 70 feet underground in billion-year-old, northern Minnesota hard granite, surrounded by 10 feet of granite rock overburden along the perimeter, and a 4-foot-thick concrete roof topped with 6 inches of barite aggregate to block potential interference from cosmic radiation. The roof incorporates a 63-foot clear span, pre-stressed concrete beam support system to accommodate movable access platforms, facilitating detector construction and maintenance.