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U.S.-German collaboration bears first fruits

PPPL-designed coil critical to experiment arrives in stellar condition

Engineers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have designed and delivered a crucial barn-door size component for a major device for developing fusion power. The component, called a “trim coil,” marks the initial installment of one of the largest hardware collaborations that PPPL has conducted with an international partner.

The 2,400-pound trim coil is the first of five coils that PPPL is producing for the Wendelstein 7-X stellarator, or W7-X, that the Max Planck Institute for Plasma Physics (IPP) is building in Greifswald, Germany. The powerful coils will fine-tune the shape of the superhot, charged gas called plasma that the W7-X will use to study conditions required for fusion when the machine begins operating in 2015.

In exchange for the coils, PPPL scientists will be able to lead and carry out experiments on the W7-X. Stellarators are one of the two major devices that scientists are using to develop fusion as a source of clean and abundant energy. The other device is the tokamak. “Stellarators offer solutions to problems facing magnetic fusion reactors that haven’t been solved in any other way to date,” said Hutch Neilson, director of advanced projects at PPPL.

Delivery of the first trim coil on June 26 capped two years of teamwork between PPPL and IPP and a final month of intense activity. PPPL engineers Mike Mardenfeld and Steve Raftopoulos , together with colleagues from IPP, made eleventh-hour trips to coil manufacturer Everson Tesla in Nazareth, Pa., when surface imperfections appeared in the epoxy-like resin that encases the copper coil. “The stakes are fairly high,” said Neilson. “Whenever you build the first of anything there are always unexpected surprises that you have to work your way through. In this case, the imperfections turned out to be nothing and were easily removed.”

Hastening the last-minute rush was the fact that all five coils are to be delivered to IPP by January 2013. “Getting the first coil out the door was very challenging,” said PPPL engineer Stephen Langish, who manages the trim coil project and monitored the first one with Mardenfeld, Raftopoulos and quality assurance expert Frank Malinowski. “We just had a very aggressive schedule.

Delivery of the coil over the 4,300-mile sea and land route to Greifswald proved no less challenging. Workers at Everson Tesla had to crate the device standing up since it was too wide to travel on German roads without a police escort. “There was enough wood in the crate to build two backyard decks,” said Greg Naumovich, the president of Everson Tesla, which is manufacturing the coils under an $800,000 contract with PPPL.

The standing crate was barely within the 13-foot height ceiling for German roads when the coil arrived in Antwerp, Belgium, from Chester, Pa., and was loaded onto a flatbed truck. Planners carefully plotted the 500-mile route from Antwerp to Greifswald in northeast Germany to avoid low highway clearances.

Safe delivery of the huge coil ended a period of anxious waiting in Greifswald. “I was relieved that the coil was not damaged, and also proud of the result of our teamwork with PPPL,” said engineer Konrad Risse, the trim coil project leader at IPP. “This collaboration was very special because the trim coils are the first large component to be provided by another scientific laboratory.”

Technicians will assemble the coils on the W7-X alongside other key parts from more than 30 companies throughout Europe. Installation of the first trim coil is scheduled to be completed in September. The coils will enable stellarator experiments to run smoothly by correcting any errors in the magnetic field that surrounds and shapes the plasma. Such corrections are essential, said Risse, since the stellarator field is very sensitive to non-systematic deviations.

Back at PPPL, engineers have completed the design of five electric power supplies that will run the W7-X trim coils when the stellarator begins operating. The project is already reviewing bids from manufacturers for the contract to produce the supplies, which are to be delivered to Greifswald by August 2013. Shipment of the parts will complete the Laboratory’s hardware collaboration with IPP, and set the stage for PPPL to prepare its own W7-X experiments.

Timely delivery of the first trim coil was thus a key step for the overall project. “It’s an important accomplishment that puts us on target to deliver all five coils in excellent fashion,” said Neilson, the PPPL director of advanced projects. “We’re probably going to come in ahead of schedule and under budget.”

U.S. Department of Energy
Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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