NOvA target arrives from Rutherford Appleton Laboratory

Rutherford Appleton Laboratory engineer Michael Fitton looks through the chamber housing the NOvA target, which comprises 48 small, upright graphite fins lined up in a row. Photo: Stephen Kill

Engineers at Rutherford Appleton Laboratory in the UK recently completed the manufacture of the target for Fermilab’s future NOvA experiment. The target, which arrived at Fermilab last month, is the outcome of 18 months of collaboration between the two laboratories and UK industry.

It’s also designed to be one of the world’s toughest production targets for a neutrino experiment.

“It’s the highest pulsed-power-density neutrino target that will see action in the world to date,” said Fermilab’s Patrick Hurh, who coordinated the accord for the NOvA target.

The target is designed to take on a 700-kilowatt beam of protons, roughly 10 times more power than was used for the Tevatron’s antiproton source target. When protons strike the NOvA target, they’ll generate particles that decay into neutrinos, which will then fly straight through the earth to a detector 500 miles away in Ash River, Minn.

Researchers constructed the target from graphite, a material strong enough at high temperatures to withstand the stress of the high proton-beam power.

Though Fermilab had previously established most of the specifications for the target design, they turned to RAL to fill in the details. Having designed and manufactured a similar target for the T2K experiment in Japan, RAL was the only laboratory in the world to have built a neutrino target to withstand an amount of beam power similar to that needed for NOvA.

“After working with Patrick and colleagues over recent years on design studies for LBNE and Mu2e, it was rewarding for Rutherford Appleton to be able to deliver a piece of real hardware to Fermilab,” said Chris Densham, who leads the High-Power Targets Group at RAL. “The NOvA target requirements were demanding, but with some development work we made one that performed well inside the specification.”

The Fermilab team is now testing alignment, meticulously recreating the mechanics of every part involved in the positioning and stability of the beam and target. As Target Lead Engineer Mike McGee notes, once the target and its associated structures are underground, there’s no going back in.

“Imagine the moment that we close off this target,” he said. “We’ll never have a line of sight to the target again.”

The experiment will begin producing neutrino beams in 2013, and researchers have RAL to thank for the element that helps make them.

“They’re like an extension of my group here at the lab. I can call them up and get answers,” Hurh said. “I’m proud of the work they did, and I know they’re proud of it.”

—Leah Hesla