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Last modified: Monday, April 30, 2012

With NOvA building complete, IU physicists, astronomer ready to construct particle detector

IU responsible for major component of $283 million experiment

April 30, 2012

BLOOMINGTON, Ind. -- The laboratory is now built, and Indiana University physicists are ready to help assemble within it the world's largest PVC structure. It's all part of NOvA, an advanced neutrino experiment designed to help explain why the universe was created with more matter than antimatter.


Fermilab Deputy Director Young-Kee Kim, left, and NOvA spokesperson Mark Messier from Indiana University tour the cavernous building that will house the 15,000-ton NOvA detector.

Print-Quality Photo

With the opening May 27 of NOvA -- the NuMI Off-Axis Electron Neutrino Appearance far detector building -- in northern Minnesota, scientists are ready to begin piecing together the 15,000-ton particle detector that will study neutrinos produced at Fermilab in Chicago, which are then sent 500 miles in under three milliseconds to the new far detector building. Among those ready to assist are 14 IU scientists responsible for the detector's most critical element, a liquid scintillator that comprises 70 percent of the total detector mass and that will be used to collect light from particle interactions in the detector.

"With the laboratory now complete, we've begun installing the major detector components," said Mark Messier, a professor in the IU Bloomington College of Arts and Sciences' Department of Physics who also serves as spokesperson for NOvA. "This includes the delivery system for the liquid scintillator, which is a major IU responsibility overseen by IU astronomy professor Stuart Mufson and physics professor James Musser."

The liquid scintillator is how physicists make the particles produced by neutrino interactions visible. The far detector will be composed of 385,000 cells of extruded PVC plastic, with each cell 3.9 centimeters wide, 6 centimeters deep and 15.5 meters long. The cells are filled with 3.2 million gallons of liquid scintillator, a material that becomes luminescent from ionized radiation. The scintillation light is subsequently guided to photo-detectors using wavelength shifting fiber.

Construction of the detector, with its 13 million pounds of PVC, begins in May, and the first components get filled with liquid scintillator later this summer, with the hope being that detector readings can begin in the fall. First results would be in the fall of 2013, and the full experiment is scheduled for completion in April 2014.

The $283 million NOvA experiment is an international collaboration of nearly 180 scientists and engineers from 28 institutions in seven countries. Once complete, the detector will allow physicists to study the behavior of neutrinos by examining pulses of the subatomic particles twice -- as they leave Fermilab's Illinois site and as they pass through the NOvA facility in Minnesota.

Because scientists still don't know the masses of the different neutrino types, or which type of neutrino is the lightest and which is the heaviest, the NOvA experiment is designed to search for oscillations of muon neutrinos to electron neutrinos by comparing the electron neutrino event rate measured at the Fermilab site near Chicago with the electron neutrino event rate measured at a location just south of International Falls, Minn., about 500 miles away. If oscillations occur, the far site will see the appearance of electrons in the muon neutrino beam produced at Fermilab and the experiment can begin to study differences in the oscillations using beams of neutrinos and antineutrinos. Matter/antimatter differences in neutrinos may be responsible for tipping the balance in favor of matter over antimatter in the early universe.

Other IU researchers working with Messier, Mufson and Musser include physics professor Jon Urheim; post-doctoral researchers Luke Corwin and Chad Johnson; graduate students Michael Baird and Evan Niner; IU physics technical staff Fritz Busch, Mark Gebhard, Brice Adams and Philip Childress; and IU Cyclotron Facility engineers Gerard Visser and Walter Fox; and Jonathan A. Karty, Mass Spectrometry Facility Manager and Metacyt Biochemical Analysis Facility Interim Director in IU's Department of Chemistry.

IU's primary responsibility has been the optimization of the scintillator cost and performance, working out the mixing and delivery mechanism, and understanding how to ensure uniform standards of production quality.

For more information, please contact Steve Chaplin, IU Communications, at 812-856-1896 or Tweeting Indiana University science news: @IndianaScience