Years from now—maybe in a decade, maybe sooner—if all goes according to plan, the most complex machine ever built will be switched on in an Alpine forest in the South of France. The machine, called the International Thermonuclear Experimental Reactor, oriter, will stand a hundred feet tall, and it will weigh twenty-three thousand tons—more than twice the weight of the Eiffel Tower. At its core, densely packed high-precision equipment will encase a cavernous vacuum chamber, in which a super-hot cloud of heavy hydrogen will rotate faster than the speed of sound, twisting like a strand of DNA as it circulates. The cloud will be scorched by electric current (a surge so forceful that it will make lightning seem like a tiny arc of static electricity), and bombarded by concentrated waves of radiation. Beams of uncharged particles—the energy in them so great it could vaporize a car in seconds—will pour into the chamber, adding tremendous heat. In this way, the circulating hydrogen will become ionized, and achieve temperatures exceeding two hundred million degrees Celsius—more than ten times as hot as the sun at its blazing core.
No natural phenomenon on Earth will be hotter. Like the sun, the cloud will go nuclear. The zooming hydrogen atoms, in a state of extreme kinetic excitement, will slam into one another, fusing to form a new element—helium—and with each atomic coupling explosive energy will be released: intense heat, gamma rays, X rays, a torrential flux of fast-moving neutrons propelled in every direction. There isn’t a physical substance that could contain such a thing. Metals, plastics, ceramics, concrete, even pure diamond—all would be obliterated on contact, and so the machine will hold the superheated cloud in a “magnetic bottle,” using the largest system of superconducting magnets in the world. Just feet from the reactor’s core, the magnets will be cooled to two hundred and sixty-nine degrees below zero, nearly the temperature of deep space. Caught in the grip of their titanic forces, the artificial earthbound sun will be suspended, under tremendous pressure, in the pristine nothingness of iter’s vacuum interior.
For the machine’s creators, this process—sparking and controlling a self-sustaining synthetic star—will be the culmination of decades of preparation, billions of dollars’ worth of investment, and immeasurable ingenuity, misdirection, recalibration, infighting, heartache, and ridicule. Few engineering feats can compare, in scale, in technical complexity, in ambition or hubris. Even the iter organization, a makeshift scientific United Nations, assembled eight years ago to construct the machine, is unprecedented. Thirty-five countries, representing more than half the world’s population, are invested in the project, which is so complex to finance that it requires its own currency: the iter Unit of Account.
No one knows iter’s true cost, which may be incalculable, but estimates have been rising steadily, and a conservative figure rests at twenty billion dollars—a sum that makes iter the most expensive scientific instrument on Earth. But if it is truly possible to bottle up a star, and to do so economically, the technology could solve the world’s energy problems for the next thirty million years, and help save the planet from environmental catastrophe. Hydrogen, a primordial element, is the most abundant atom in the universe, a potential fuel that poses little risk of scarcity. Eventually, physicists hope, commercial reactors modelled on iter will be built, too—generating terawatts of power with no carbon, virtually no pollution, and scant radioactive waste. The reactor would run on no more than seawater and lithium. It would never melt down. It would realize a yearning, as old as the story of Prometheus, to bring the light of the heavens to Earth, and bend it to humanity’s will.iter, in Latin, means “the way.”
The main road to the iterconstruction site from Aix-en-Provence, where I had booked a room, is the A51 highway. The drive is about half an hour, winding north past farmland and the sun-glittered Durance River. Just about every form of energy is in evidence nearby, from hydroelectric dams to floating solar panels. Seams of lignite, a soft brownish coal, run beneath the soil in Provence, but the deposits have become too expensive to mine. Several miles from Aix, a large coal plant, with a chimney that climbs hundreds of feet into the sky, is being converted to burn biomass—leaves, branches, and agricultural debris. iter is being built a mile or two from the wooded campus of the Commissariat à l’Énergie Atomique et aux Énergies Alternatives, a state-funded research organization, created in 1945 to advance nuclear power, and now also renewable energy. Evergreen oak and Aleppo pine cover the foothills; beneath them, the French government maintains its largest strategic oil reserve.
iter’s headquarters, a five-floor edifice, was erected two years ago. An undulating wave of gray concrete slats shade its floor-to-ceiling windows. Its interior is simple: whitewashed walls, polished-concrete floors. The building’s southern façade overlooks a work site, more than a hundred acres of construction on the opposite side of a berm. By the time the reactor is turned on—the formal target date for its first experiment is 2020—the site will be home to a small city. Nearly forty buildings will surround the machine, from cooling towers to a cryogenics plant, which will produce liquid helium to cool the superconducting magnets. A skywalk extends from the second floor of the headquarters to the berm, where a capaciousnasa-style control room will one day be built. For now, the bridge ends in a pile of ochre dirt, and the only way to the vast expanse of construction is via a circuitous drive.
When I arrived, on a late-summer morning, the air was dry and warm—filled with the aroma of pine, lavender, and wild thyme. Five hundred people work for iter’s central organization, but an unusual sense of quiet and vacancy permeated the place; this was August in France, and many workers had taken time off. The atmosphere seemed to be drawn from the imagination of J. G. Ballard: the modernist husk of a utopian project, half-finished, half-populated, isolated amid a primeval forest. A few people with clipboards stood beneath the sun to map out an expansion to the headquarters. To save money, an entire wing had been abandoned during the construction, and employees worked out of temporary annexes—their staircases and walls hollow, like stage sets—built several hundred yards away, with shuttle buses moving among the buildings. The busing has proved to be impractical, and so the wing will be constructed after all, though now at greater expense.
In a bare lobby, I wandered over to a model of the reactor core: a cylinder, dense with mechanical parts, rendered in brightly colored bits of machined plastic. iter’s design is based on an idea that Andrei Sakharov and another Russian physicist, Igor Tamm, sketched out in the nineteen-fifties. It is called a tokamak—old Soviet shorthand for a more precise and geometrical name, toroidalnaya kamera s aksialnym magnitnym polem, or “toroidal chamber with an axial magnetic field.” Sakharov’s rough sketch depicted a doughnut-shaped vacuum chamber, or torus, ringed with electromagnets, and that is how iter’s core will look, too, once it is completed.
In myriad ways, the project is a fragment of the Cold War stranded in the present day. Sakharov had predicted that a reactor based on his sketch would produce energy in only ten or fifteen years. Subsequent physicists who built and ran experimental tokamaks were equally optimistic, always predicting success in a decade or two or three. Yet, while other scientific challenges have been overcome—launching Yuri Gagarin into orbit; delivering a rover to Mars; sequencing the human genome; discovering the Higgs boson in cern’s Large Hadron Collider—controlled thermonuclear energy has remained elusive. The National Academy of Engineering regards the construction of a commercial thermonuclear reactor—the kind of device that would follow iter—as one of the top engineering challenges of the twenty-first century. Some in the field believe that a working machine would be a monument to human achievement surpassing the pyramids of Giza.
iter was first proposed in 1985, during a tense summit in Geneva between Ronald Reagan and Mikhail Gorbachev, who agreed to collaborate “in obtaining this source of energy, which is essentially inexhaustible, for the benefit for all mankind.” Since then, the coöperation has expanded to include the European Union, China, Japan, South Korea, and India. In the iter lexicon, each partner is a Domestic Agency. Unlike any previous scientific collaboration, no partner has full control, and there is no over-all central budget. Each country makes its primary contribution in the form of finished components, which the iter organization will assemble in France. The arrangement could serve as a model for future collaborations—or as one to avoid. At the headquarters, there is a circular dais, where representatives from the Domestic Agencies come and sit, with flags and placards before them, like members of the U.N. Security Council. But there are limits to diplomacy in nuclear engineering. Big machines either work as they’re supposed to or they don’t. Compromise and politesse can be disastrous. Thousands of components—many of them huge machines in their own right—must be slotted beside one another, more or less perfectly, and there will be scant ability to correct imperfections after they are delivered. Ultimately, the project’s success may rest on a simple question: Will everything fit together?
Stefano Chiocchio, iter’s head of design integration—its chief puzzle master—works in one of the temporary annexes near the headquarters. His BlackBerry typically contains an impossible schedule of overlapping appointments, forcing him to conduct meeting triage as he rushes around like a zigzagging atomic particle. Rather than take the shuttle among the buildings, he drives his car to save minutes. When he speaks, he often gets halfway through a sentence, stops, and says, “O.K.”—ending his thought right there. Sometimes a friend will stop him mid-stride, and say, “Stefano,” and smooth out his rumpled collar.