Prager also is calling for patience among his own staff. As one of the Energy Department’s 10 scientific national laboratories — and the only one completely devoted to fusion — PPPL’s place is secure; its staff of 425 and its $81 million budget haven’t changed in half a decade. Some in the lab want Prager to lobby for a major project to replace the void left by the NCSX cancellation. But instead of putting all the eggs in a single basket, Prager is preaching diversity: He wants PPPL to pursue projects of different sizes — small, medium, and perhaps large — and to concentrate on developing niche expertise. The brainpower, rather than the machine power, is what is important, he believes. As longtime PPPL scientist Ned Sauthoff, who now leads U.S. ITER efforts at Oak Ridge National Laboratory in Tennessee, says, “Research institutions should not be owned by their iron.”  

PPPL already is pursuing a handful of small-scale experiments that cost on the order of $10 million. One with particular promise is the Lithium Tokamak Experiment (LTX), a spherical torus small enough to fit in a pickup truck. Almost accidentally, it was discovered that lithium — that age-old treatment for depression — also seemed to have a way of soothing red-hot plasmas. “It was almost like throwing cold water into the plasma,” says LTX scientist Phil Efthimion. The lithium allowed for a thicker, more manageable plasma and longer burns. A previous version of LTX just used a tray of solid lithium at the bottom of the tokamak, but Efthimion is now working to run LTX with a thin liquid coating of lithium clinging to the entire tokamak wall — which could further enable lithium’s seemingly magical powers. “It could have a big impact,” he says.

Around the medium range — on the order of $100 million — are experiments such as NSTX, which was like the yin to the stellarator’s yang. When NCSX was canceled, the spherical experiment was given the green light for continued operations and today is in the running for a major upgrade, which would double the strength of its magnetic coils. For now, NSTX project director Masayuki Ono *78 says, the team is trying to make the most of 2009’s 16 weeks of approved operation. “It’s still relatively new. We’re gaining confidence every day.” Of course, many at PPPL still nourish the dream that NCSX will be resurrected — one reason why the lab mothballed the parts so carefully. While Germany and Japan are each building a stellarator, no other facility in the United States has embarked on a big one, and the particular issues explored by stellarators have not disappeared.  

But PPPL lacks a large, billion-dollar project on the scale of the machine it had in the 1990s with TFTR. And, Prager notes, it’s unlikely to get anything like it in the near future. But that shouldn’t stop the lab from planning for one. Former director Goldston, who has remained on the staff to — among other things — lead PPPL’s ITER involvement, already has an idea. ITER is expected to produce 500 megawatts of power in bursts of fusion lasting six to seven minutes — a major step, but still short of the 2,500 megawatts that a demonstration fusion power plant would be expected to produce continuously. In ITER, hot particles from the plasma slam into a particular part of the tokamak called the diverter — and the diverter barely can handle it. Diverters are expected to wear out quickly. “The technology has to change,” says Goldston, who wants to build a small tokamak that mimics the high power of a demonstration reactor. PPPL then would use its expertise with lithium technology to experiment with the materials and technology needed to withstand those conditions.  

Goldston notes that the most of the other nations that have signed on to ITER — Korea, China, and India — have major fusion reactors in the works. The United States does not, and all of its big operating facilities are several decades old. Fusion funding from the Department of Energy stands at $500 million for fiscal year 2009 — less, in real dollars, than the United States spent in the early 1980s, and less than Japan and the European Union spend today. Goldston compares the situation to a Texas Hold ’Em poker game. Just as poker players take advantage of the community cards at the center of the card table, everyone is poised to benefit from the technology advances of ITER. But to win at poker, you also need decent “hole cards” that are yours alone. Other nations, Goldston says, have their hole cards. “Nobody in the history of Texas Hold ’Em poker has ever won without some hole cards,” he says. “What’s the U.S. going to do for its hole cards?”

Eric Hand ’97 is a writer for the journal Nature.

It has been a long road for ITER, the machine that could bring the fusion burn of the sun to a place not too far from the French Riviera. But if it is to succeed, there may be a detour along Route 1 to pick up a few parts made in New Jersey.  

Originally conceived in 1985, ITER stands for International Thermonuclear Experimental Reactor. Since “thermo-nuclear” tends not to get the best public relations — the word seems to suggest a bomb, rather than a balm for mankind’s energy troubles — officials refer to ITER by its acronym alone, noting that ITER is Latin for “the way.”  

But “the way” has been littered with obstacles. For many years, politicians couldn’t even decide on a place to put it, primarily because of squabbling between Japan and France, each of which wanted to host it. Finally, in 2006, seven parties — the United States, the European Union, Russia, China, India, Japan, and Korea — signed a treaty that officially formed ITER. Clearing at the selected French site, in Cardarche, has begun, and construction is expected to start next year, with experiments beginning by the end of the next decade. But the €10 billion price tag estimated in 2001 — about $13 billion — could end up nearly doubling in a revision due before the end of this year. And a new problem controlling the plasma is forcing designers to add another layer of magnets at a late stage.  

ITER’s doughnut-shaped tokamak design calls for giant superconducting magnets to keep a handle on hydrogen plasma heated to temperatures of 100 million degrees Celsius. ITER — by far the biggest fusion reactor ever attempted —- would be the first to reach “ignition” and “burn,” the point at which heat created from fusion is sufficient to sustain the reaction.  

With fusion budgets that have been smaller than those in other participating nations, the United States never really was in the running to host ITER. Still, PPPL was, for many years, the locus of this country’s ITER involvement. Then, at the beginning of 2006, two years before the stellarator was axed, the Department of Energy decided to move U.S. ITER headquarters from PPPL to Oak Ridge National Laboratory in Tennessee. PPPL lost U.S. ITER director Ned Sauthoff, a longtime employee who decamped for Tennessee. “I’m sure that Princeton would have liked to have kept its position as lead and host [for ITER],” says Sauthoff, who attributes the Energy Department’s decision to Oak Ridge’s project-management experience in completing a major neutron-beam facility. To stay influential on ITER, Sauthoff says, Princeton will have to carve out niches, specializing in smaller, but still crucial, activities.  

A good example of the Princeton lab’s relevance lies in the latest issue ITER’s designers have encountered: ELMs, an innocuous-sounding acronym — but potentially devastating problem — that stands for Edge Localized Modes. ITER’s huge size helps it contain larger plasmas at higher temperatures, but it also means the plasma is more unruly. An ELM, a particular type of plasma turbulence, is like a puncture wound at the edge of what is supposed to be a smoothly confined plasma wall.  

Wearing a hard hat, Masayuki Ono *78 walks into the control room at the Plasma Physics Lab for the spheroidal torus experiment (NSTX). He opens his laptop to show what an ELM is like. Ono plays a video of a few seconds of NSTX operations, captured by a camera capable of gathering 100,000 frames per second. The video frames are like global X-rays of the sphere. All is quiet and black until a burst of light suddenly appears in one corner and spreads, blanching the globe in white. “You see it brighten up?” asks Ono. “That was an ELM.” In a fraction of a second, the ELM deposits about 20 kilojoules of energy — 10 percent of the NSTX’s output — into the machine’s wall. That’s less than the heat energy in a teaspoon of gasoline, so the NSTX can handle it, says Ono. But ITER may spew ELMs a thousand times more destructive, tossing out the equivalent of a few hand grenades every second. “You can imagine what that would do to the walls,” he says.  

The modest size of NSTX, and its shape, make it well-suited for experiments into damping the ELMs. Ono walks through a chilly concrete tunnel that connects the control room to the NSTX. The sphere sits on stilts and is barely visible, camouflaged in a jungle of hardware that is used for experiments. Within the tangle, hidden along the equator, lies a potential solution to the ELM problem: another set of magnets, shaped like rectangular windows. These create something like perforations in the magnetic wall containing the plasma, softening it up so that energy bleeds out smoothly rather than building up into the burst of an ELM. PPPL engineers have been commissioned to design and build the window magnets for ITER. “This is the big new complicated thing that has to be put on ITER,” says former PPPL director Robert Goldston *77, “and we’re doing it.”