Detecting the unseen

University students are building parts for a neutrino detector in hopes of helping scientists explain the origin of the universe.
Senior civil engineering major Dan Grannes performs a final inspection on a neutrino detector module Thursday at the NOvA project's Como warehouse. After passing inspection, the panels will be shipped to the Fermi National Accelerator Laboratory in Illinois.
August 06, 2010

 

Leaning up against a table, Christian Kluge  stared intently at the work in front of him, pencil in hand. Metallic pings and the buzz of sawing and welding bounced off the walls of the enormous warehouse, but he remained focused.
Building a machine that can detect miniscule particles is no easy feat. When those particles may hold answers to how the universe was created, Kluge’s work has even more weight.
“If we screw up, then they’re not going to ever find anything,” the fifth-year aerospace engineering major said. 
Kluge was just one of 20 students working at the NOvA warehouse in Southeast Como, where University of Minnesota students have been helping to build two neutrino detectors.
The work for the first detector, called the near detector, is almost finished and is being installed at Fermilab, a physics research facility just outside of Chicago.
The NOvA warehouse will be bustling in the coming months, as more than 100 students begin construction for its big brother, a 15,000-ton far neutrino detector to be installed in a new lab near International Falls.
Research there is expected to begin at the end of 2013, NOvA spokesman Mark Messier  said. The near detector will be operational by October.
The warehouse is financed as just a fraction of the $300 million grant from the Department of Energy that made the NOvA project possible.
A neutrino is an abundant particle with a small mass and no electric charge that moves at nearly the speed of light.
“Because they don’t have charge, they hardly interact with anything at all,” said Ken Heller, associate head of the physics department at the University and NOvA manager. ”Most of them cruise right through the earth.”
And, unbeknownst to humans, right though our bodies. But the few interactions that neutrinos do have may hold the key to the origin of the universe.
There are three types of neutrinos, each of which transform to a different neutrino type over time and space. The most elusive of those transformations, or oscillations, is from muon to electron neutrinos. That’s what the NOvA detectors are setting out to observe.
The universe can only exist because of an asymmetry between matter and anti-matter: the laws of physics dictate that when matter is created from energy, an equal amount of anti-matter is created.
The oscillation from muon to electron neutrinos could explain why that asymmetry exists.
It’s a lofty goal, and Heller said it might not be possible. If not, the researchers at Fermilab will still gain valuable knowledge about neutrinos in general.
 
Building a neutrino detector
“These guys are ready to be shipped out,” Heller said, pointing to a stack of nondescript PVC panels. Though they look unremarkable, these panels are the heart of the near detector.
Inside those roughly 10 foot panels are 32 cells, each of which is filled with mineral oil and a string of fiber optic cable. A stack of about 500 of those panels glued together will make up the near detector.
The far detector is made of panels — called modules — that are about 32 feet long.
When the beam at Fermilab fires neutrinos to each detector, the fiber optics inside will pick up the byproducts of the interactions and feed them to a photo detector on each module, which will send the data to a computer for readings.
“By what stuff it makes, we can tell which kind of neutrino it is,” Heller said.
On days of steady production, students work in teams at six different stations. Gluing halves of each module together, stringing fiber optics through each cell and pressure testing each module for leaks are just parts of the process.  
Seated at a large table with three other students, mechanical engineering senior Katherine Black  worked a razor into a metal mold to pull out a silicon suction cup. Vacuum-powered machines use those suction cups to move and stack the finished modules.
“I get the practical, hands-on side of things,” she said. “I get to learn how to weld and put things together, and I think that’s really helpful in my major.”
From the suction-cupped machines to the intricate pulley system that strings the fiber optics, nearly every piece of machinery inside the warehouse was designed and built by the students.
Despite the fact that the theory behind a neutrino detector is rooted in physics, engineering majors are right at home at the NOvA warehouse on campus. Every step in the build process presents a problem that engineers can design a solution for.
“It gets me to think out of the box, and I get to design things whenever I get a free moment,” said Christian Kluge, who has been working there since production for the near detector began.
While the University builds the skeleton of the neutrino detectors, it is just one piece of the NOvA puzzle. Twenty-seven other universities from across the globe are contributing to the process in other ways.
Indiana University  is responsible for blending the mineral oil for each cell of the detector, and Harvard University  and the California Institute of Technology will deal with the electronics.
“It is somewhat unique in that things typically are done by lab technicians and lab staff,” NOvA spokesperson Mark Messier said of the University’s involvement in the project.
There are just a handful of lab technicians and faculty on duty at the University warehouse.
“The bottom line of it is that they do very good work and they’re very cheap in relation to the technicians,” Messier added.
Students are paid between $10 and $13 per hour and work a minimum of 10 hours per week.
 
Forging ahead on the far detector
The students at the University’s NOvA warehouse are getting a bit of a breather, but it won’t last long.   
Production on the far detector will begin at the start of 2011. In the meantime, more than 100 additional students will be hired to help prepare for a much heavier workload.
 The warehouse churned out about 10 modules per day while working on the near detector. They’ll need to triple productivity in order to stay on schedule for project completion.
“That will continue for two and a half years, because there’s a lot to make,” Heller said.

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