A cutaway view of the MIT team’s conceptual ARC design. The doughnut shape is consistent with existing fusion reactor designs; the relatively small size and modular nature of the components are notable. Advances in magnet technology make it theoretically possible for a device of this size to efficiently confine plasma at its center while heating it to temperatures exceeding that of the sun’s center. Illustration: Chris Philpot
PHOTO ILLUSTRATION: CHRIS PHILPOT
Nuclear fusion, the reaction that powers the sun, could offer a near-inexhaustible energy source on Earth. The longstanding challenge has been to design a fusion reactor that produces more energy than it consumes, and that won’t require decades and billions to build. The ARC design is remarkable for at least two reasons: it has the potential to surmount those obstacles—and it began as a class project.
The director of MIT’s Plasma Science and Fusion Center (PSFC) and head of the Department of Nuclear Science and Engineering, Dennis Whyte, teaches 22.63 Engineering Principles for Fusion Reactors every two years to a mix of undergrads and grad students from such departments as nuclear science and engineering, physics, mechanical engineering, and electrical engineering and computer science. Rather than assigning problems with known solutions, Whyte puts their intellects and imaginations to work on some of the loftiest real-world goals in nuclear engineering.
Last year’s ARC paper, published in Fusion Engineering and Design, was no fluke. The previous 22.63 had yielded five peer-reviewed papers. This semester, the class’s dozen or so students are hammering out critical details of ARC’s interior design. On a Tuesday this past March, the discussion centered on cooling channel geometries and alternatives to tungsten. Whyte sat toward the back of the classroom while Team Magneto and Team Molten Man presented their findings. (The comic-book motif is a running joke; ARC itself references an invention by fictional MIT alum Tony “Iron Man” Stark.) Whyte listened quietly at first, then jumped in with queries or to prompt a new line of thinking. Other visitors—a research scientist, a couple of professional engineers—chimed in with pros and cons for various design options. As everyone packed up at the end of class, Whyte was visibly excited: “I can’t tell you how pumped up I am about a neutron-shielded divertor!”
How is it that such promising insights can originate in a classroom, when seasoned professionals are hard at work down the street—and across the ocean—on the same problems? Whyte says his students go down plenty of blind alleys, but have a knack for challenging baked-in assumptions. “Young people don’t have what I call the ‘everybody knows’ syndrome,” he says. “‘Everybody knows this is how you build a magnetic coil’—they’re not saddled with that, yet they’re very skilled. That’s exactly the way you open up new research venues.”
When Andrew Revkin of the New York Times commented on the ARC paper, “It’s exciting to see academia integrating directly with innovation on this scale,” he was zeroing in on a key feature of PSFC: its research and education activities are closely interwoven because they are mutually beneficial.
Whyte can recall at least three moments in last year’s ARC class that he considers “major breakthroughs . . . clever engineering choices that, if they could be implemented, would be groundbreaking to the whole field.” He points to the modular nature of the ARC design, which allows its coils to be taken apart and more easily modified and repaired. “That was a student’s idea. Everybody knows you can never demount superconducting magnets—except you can, as it turns out.”
PSFC researchers are already moving forward with an adapted ARC design. The paper, Whyte says, “was an affirmation of the pathway we are already going down with our research program [the Alcator C-Mod tokamak reactor, operating at MIT since 1991]. It gave the whole lab a better sense of the possibilities.”