CAMBRIDGE, Mass. — This is what a fusion lab is supposed to be like. As I walk in, a woman’s voice is on the speakers, counting down from ten. Banks of chairs face banks of computer monitors, where data is literally streaming across application windows that are pulsing, multi-colored and reassuringly complex. And at the head of the control room is a massive projection showing a diagram of the fusion chamber nearby—a top-down view of the donut-shaped, concrete-lined structure that’s about to fill with superheated ionized gas, or plasma. On the same wall is looped footage of the last “shot,” a brief attempt to harness that plasma, and make fusion a little more feasible. The countdown is over, and there’s a sound straight out of sci-fi—a high tone coupled with a deep, resonating hum. On a tiny, black-and-white monitor mounted on the ceiling, a one-second flash ripples across the screen. A sign lights up over the door leading to the chamber, indicating that the oxygen is too low for anyone to approach without breathing gear, and the clock starts again. Next shot in 15 minutes.MIT’s Plasma Science and Fusion Center (PSFC) is about as Hollywood-worthy as science gets. The stakes, after all, could hardly be higher. If fusion can be perfected, it could mean a golden age for power production, with systems providing all of the benefits of nuclear reactors—but none of the drawbacks. Fusion is, to some extent, the exact opposite of fission: Instead of splitting atoms, fusion combines them, creating larger atoms and releasing a massive amount of energy in the process. Despite the high temperatures often associated with plasma, fusion is a relatively stable reaction, generating little to no radioactive waste. Even in a worst-case scenario, there’s no chance of a fusion reactor turning into a catastrophe on the scale of Three-Mile Island or Chernobyl. “Fission can run away,” says Miklos Porkolab, director of the PSFC. “Fusion can only fizzle.” Since there’s no chain reaction at work, the biggest danger associated with fusion is a temperature collapse. And even if the materials lining the chamber were to suddenly give way due to sabotage or terrorism, the introduction of debris into the plasma cloud would actually smother the process at an even faster rate. Fusion is fragile, difficult to maintain, and ultimately its own worst enemy. But it is not dangerous.
That quality makes it utterly useless as a weapon, Porkolab explains, which is why the federal government decided to declassify its fusion research 50 years ago and make the results public. That was effectively the birth of open, academic fusion in the United States. So a half-century into this quest for one of science’s holy grails, are we any closer to grace?
The answer, not surprisingly, is mixed. Here at MIT, the fusion center’s primary research tool is the Alcator C-MOD, the largest university-run fusion reactor in the world, and one of only three “tokamaks” in the country. Tokamaks are reactors that use magnetic fields to control the flow of plasma. Extreme machines like the C-MOD, which has the most powerful magnetic fields of any tokamak (and some 100,000 times stronger than the Earth’s) have enhanced our understanding of fusion. But a truly efficient reaction, with more energy released than poured in, is still decades away.
The problem, Porkolab says, is turbulence. To increase the chances of a fusion reaction, a cloud of plasma must be incredibly hot and dense. As the atoms become more closely packed and excited, the natural tendency for nuclei to repel each other can be overcome. C-MOD uses microwaves to heat the ionized gas, and magnets to shape it, building up pressure within the plasma. But as any meteorologist can tell you, juggling temperature and pressure is a recipe for bad weather. “We have our own storms, inside the plasma, just like in the atmosphere,” Porkolab says. Temperature gradients within the plasma can lead to eddies, and the more unstable the cloud becomes, the more heat it loses. When the temperature gets low enough, the reaction dies. Plasma turbulence, in other words, is the biggest obstacle to fusion, limiting current reactors to brief pulses and preventing the kind of long-term reaction necessary for true power production.
That's why, when the next countdown begins in the control room, and I try to catch the real-time flash of the plasma shot on that tiny ceiling-mounted monitor, it’s gone before my camera can even focus. The replay starts to loop on the main screen—a slightly misleading bit of pyrotechnics, since the visible light released by the shot is generated at the edges of the plasma donut, where temperatures are at their lowest, and where fusion is not likely to occur. And while it’s possible that C-MOD’s pulses could one day last longer than seconds, this particular tokamak won’t reach the promised land. In many ways, C-MOD’s most important job is to pave the way for a reactor 10 times its size, called ITER.
The product of an international collaboration, ITER will be the world’s largest tokamak, and according to MIT’s Porkolab, it will be capable of pulses as long as 8 minutes, generating up to 500 MW of power (the most powerful tokamak, Britain’s JET, tops out between 10 and 20 MW). The jointly developed reactor will have roughly the same shape as C-MOD, but with 1000 times more volume in its chamber, and radio-frequency arrays operating at much higher frequencies. The goal for ITER is a self-sustaining reaction, where the plasma cloud remains stable and intact for long periods. For that to happen, scientists like Porkolab are using supercomputers to more precisely model plasma turbulence, and to develop novel methods of avoiding it. One technique is to go beyond simply surrounding the cloud with magnetic fields and slice it into cross-sections, creating layers that flow alongside each other, similar to the titanic superheated clouds on Jupiter. This process can break up the eddies that lead to instabilities, and create a more sustainable environment for fusion.But even ITER, which is scheduled to be built within 8 to 10 years, is intended as a research facility—not as an answer to our current energy dilemma. It might produce an overall surplus of energy, but it won’t be cost-effective production. For that, Porkolab estimates we’ll have to wait for ITER to show results, possibly in the 2020s, and then wait another decade or so while demo reactors are built. That means we’d see economically feasible fusion power by 2035, at the earliest, and increasingly efficient commercial reactors somewhere in the middle of the century.
Even that protracted timeline now appears optimistic. Since 2006, when seven member countries committed to the ITER’s $14.6 billion budget, federal funding for scientific research in the United States appears to have bottomed out. The U.S. agreed to pay 9.1 percent of the project’s total cost—but of the $160 million contribution planned for this year, Congress has approved just $10.7 million. “I’m laying off twelve ITER engineers,” Porkolab says, “and I can’t even get them severance pay.”
The C-MOD reactor is also limited by shrinking science funds. With more financial support, it could operate for 24 weeks out of the year. “Progress is very slow. We’re only running about half the time,” Porkolab admits. The work is likely to slow even further because of nationwide cuts to high-energy physics programs; such cuts have already led to 200 layoffs at Fermilab, a Dept. of Energy-funded particle accelerator in Illinois. If belts are in need of tightening, it might seem reasonable to limit research that appears to be wandering on the fringes. But when the primary goal of fusion is a revolution in clean energy, and the rest of the world is preparing to take a historic step in that direction, scientists fear it’s a particularly dangerous time to limit C-MOD and effectively pull out of ITER.
But even if C-MOD never reaches its full research potential, there’s more than one way to cook a plasma donut and scientists are also working feverishly on those. I leave C-MOD’s eerily perfect control room, with its starship-computer voice and distant, periodic generator rumble, for an entirely different set of pop-culture associations. Deeper, more subterranean, is a three-story-tall jumble of stainless steel—a mad scientist’s vision called the Levitating Dipole eXperiment, or LDX. Through grates in the floor, I can see researchers in hardhats weaving among the cables on the level below. In this reactor, the process of fusion confinement is complicated even further—a superconducting ring is lowered into the center of the chamber, where it levitates within the plasma. The resulting magnetic field is closer to the kind of field produced by planets like Jupiter. This project, which is a collaboration between MIT and Columbia University, is currently the only fusion experiment in the United States that uses the same kind of superconducting magnets that ITER will use. The project achieved a successful levitation this past November; unfortunately, there will be no levitation today, no plasma ignitions or ominous countdowns. For the LDX, glimpses of plasma—and the holy grail within—are few and far between
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