NOvA team assembling near-detector blocks at CDF

PPD technicians construct detector blocks for the NOvA near detector in the CDF building. Photo: Reidar Hahn

Fermilab scientists, engineers and technicians working on the NOvA near detector recently began assembling the neutrino detector blocks at the CDF building.

It’s a milestone accomplishment, said near-detector Project Manager Ting Miao. The near detector being constructed at Fermilab will be able to pick up on muon neutrinos sent from the NuMI beam, which originates at the laboratory and passes through NOvA’s second, far detector in Ash River, Minn. The near detector will also be able to define background noise that will be eliminated while analyzing far-detector data.

“It’s an exciting time now for scientists and engineers working on the detector,” Miao said.

Each block comprises 24 long, rectangular plastic layers known as modules. The blocks are nearly identical to the ones that make up the 14,000-ton far detector, but are one-twentieth the size and weigh much less. Each module contains rows of hollow tubes that will be filled with liquid scintillator solution and fiber optic cables to detect charged particles resulting from neutrinos interacting in the solution.

Scientists and engineers have spent the past month obtaining safety approvals to operate a giant, 20-foot-long glue machine that spreads adhesive on the module surfaces.

The machine, developed and built by NOvA collaborators at Argonne National Laboratory, handles the fragile modules with care while also applying the fast-drying glue. Spreading glue on a module’s surface, transporting it and stacking it on top of other modules takes less than 20 minutes—any longer and the glue will dry out, said Detector Assembly Quality Assurance Manager Xuebing Bu.

A set of steel plates will then apply pressure to the stacked modules to ensure a tight fit.

But handling the modules is not as easy as it sounds, Bu said.

“The plastics are flexible and difficult to move around, and the glue we are using has a short curing time,” Bu said. “We need to have the correct equipment to operate efficiently while also meeting safety standards."

Applying pressure to the stacked modules is also a delicate task. The team follows well-defined procedures to avoid the plastic experiencing extra stress from being lifted and moved around, Bu said.

Soon the team will begin transporting the blocks from the CDF building to the MINOS service building and eventually into the NOvA cavern 300 feet underground.

It may take an entire day to drive the blocks to the site without cracking any of the detector layers, Miao said.

“The plastic we’re using is well-suited for the experiment, but very fragile,” Miao said. “Transporting the blocks will be a big hurdle to cross.”

But if all goes smoothly, the NOvA detectors could yield precise neutrino measurements by early next year, Miao said.

“NOvA’s level of complexity and sophistication are now comparable to detectors in fixed-target and collider experiments. This detector is built for precision measurements of neutrinos,” Miao said. “We are looking forward to the steps that lie ahead.”

Sarah Khan