Machinery of an Energy Dream, The Challenge: How to Keep Fusion Going Long Enough

Courtesy of The NY Times. By KENNETH CHANG

LIVERMORE, Calif. — Fusion, the process that powers the sun, is the forever dream of energy scientists — safe, nonpolluting and almost boundless. Even here at Lawrence Livermore National Laboratory, where the primary focus of fusion work involves nuclear weapons, many scientists talk poetically about how it could end the world’s addiction to fossil fuels.

“It’s the dream of the future, solving energy,” said Stephen E. Bodner, a retired physicist who worked on fusion at Livermore in the 1960s and ’70s, recalling that the military focus was basically a cover story, a way to keep government money flowing to the lab for energy research.

“Everyone was winking,” he said. “Everyone knew better.”

The basic concept behind fusion is simple: Squeeze hydrogen atoms hard enough and they fuse together in helium. A helium atom weighs slightly less than the original hydrogen atoms, and by Einstein’s equation E = mc2, that liberated bit of mass turns into energy. Hydrogen is so abundant that unlike fossil fuels or fissionable material like uranium, it will never run out.

But controlled fusion is still a dream, avidly pursued and perpetually out of reach. Scientists have never figured out a way to keep a fusion reaction going long enough to generate usable energy. The running joke is that “fusion is 30 years in the future — and always will be.”

Now, however, scientists here have given the world some hopeful progress. Last month, a team headed by Omar A. Hurricane announced that it had used Livermore’s giant lasers to fuse hydrogen atoms and produce flashes of energy, like miniature hydrogen bombs. The amount of energy produced was tiny — the equivalent of what a 60-watt light bulb consumes in five minutes. But that was five times the output of attempts a couple of years ago.

When a physicist named Hurricane generates significant bursts of fusion energy with 192 mega-lasers, the Twitterverse revels in the comic book possibilities.

“Wasn’t he in X-Men?” one person tweeted.

“Awesome science story, but there’s a zero percent chance that a fusion laser scientist named Dr. Hurricane isn’t a supervillain,” another chimed in.

Actually, Dr. Hurricane, 45, is more Clark Kent than superhero. Instead of saving the world, his ambition is to explore the scientific puzzle in front of him.

He said it was too early to speculate about future laser-fusion power plants, and tried to deflect credit to the more than 20 scientists on the team. “I don’t want it to be about me or my funny name,” he said.

The fusion reaction occurred at the National Ignition Facility, a Livermore project with a controversial and expensive history. After the United States ended underground nuclear testing in 1992, lab officials argued that some way was needed to verify that the weapons would work as computer models said they would. The National Nuclear Security Administration, part of the Department of Energy, agreed.

The key to the facility is its middle name — ignition. For simplistic government purposes, ignition was defined as a fusion reaction producing as much energy as the laser beams that hit it. To achieve that, an initial smidgen of fusion has to cascade to neighboring hydrogen atoms.

The center of NIF is the target chamber, a metal sphere 33 feet wide with gleaming diagnostic equipment radiating outward. It looks like something from “Star Trek.” Indeed, it has been in “Star Trek,” doubling as the engine room of the Enterprise in last year’s “Star Trek Into Darkness” movie. (NIF’s vast banks of laser amplifiers also served as a backdrop for a starship commanded by a renegade Starfleet admiral.)

The laser complex fills a building with a footprint equal to three football fields. Each blast starts with a small laser pulse that is split via partly reflecting mirrors into 192, then bounced back and forth through laser amplifiers that fill a couple of warehouse-size rooms before the beams are focused into the target chamber, converging on a gold cylinder that is about the size and shape of a pencil eraser.

The laser beams enter at the top and bottom of the cylinder, their heat generating an intense bath of X-rays that rushes inward to compress a peppercorn-size pellet. The pellet contains a layer of carefully frozendeuterium and tritium, the heavier forms of hydrogen, and in a brief moment — about one ten-billionth of a second — the imploding atoms fuse together.

The scientists call it bang time.

Each shot is so short that the cost in electricity is just $5.

Livermore officials were confident enough that NIF would achieve ignition soon after it was turned on that they laid out a plan for building a demonstration power plant, called Laser Inertial Fusion Energy with the appealing acronym LIFE, technology they said could be ready for the world’s electrical grids by the 2030s.

Dr. Bodner, who had left Livermore in 1975 and set up a competing program at the Naval Research Laboratory, was a persistent critic of NIF. In 1995, he wrote a paper predicting that instabilities in the imploding gas would thwart ignition.

“Why did they go forward with something that failed almost immediately?” he said in an interview.

Dr. Bodner championed a different laser fusion concept that he believed would work far better for a power plant. The gold cylinder in Livermore’s design is inefficient. Not all of the laser energy is converted into X-rays; most of the X-rays miss the pellet. Only 0.5 percent of the laser energy reaches the fuel.

In Dr. Bodner’s designs, the lasers shine directly on the fuel pellets. That creates other technical difficulties, but Dr. Bodner said his team was able to show those could be overcome. He retired in 1999.

NIF began firing its lasers in 2009. A banner unfurled on the outside of the building proclaimed, “Bringing Star Power to Earth.” But for all of the technical wizardry, the first three years of bang time were largely a bust.

Livermore’s computer simulations had predicted robust implosions leading to ignition. Instead, each pellet released just a bit of energy. Livermore officials remained publicly confident. Edward Moses, then NIF’s director, told the journal Nature, “We have all the capability to make it happen in fiscal year 2012.”

It did not happen. The cost of building and operating NIF to date is $5.3 billion.

In stars like our sun, the immense gravity provides the squeeze that enables fusion. On earth, there are two main possibilities: powerful lasers to jam the hydrogen together, as at NIF, or magnetic fields to contain a hot hydrogen plasma until the atoms collide and fuse. Most fusion energy research has focused on the latter approach, particularly doughnut-shaped machines known as tokamaks.

From the 1970s to the mid-1990s, the amount of power produced by ever larger machines doubled every year, on average. In 1994, the Tokamak Fusion Test Reactor at Princeton generated 10.7 million watts of powerfor a brief moment. Three years later, the Joint European Torus in England topped that, at 16 million watts.

But by then, without an immediate energy crisis, government financing of fusion research had dipped sharply.

The next step is a mammoth international collaboration known asIter, originally an acronym for International Thermonuclear Experimental Reactor, but now referring to the Latin for “the way.” Construction on Iter has begun in southern France, with the first operations expected to begin in the 2020s — if it comes together.

Under a byzantine, dispersed management structure, the partners in the project (the European Union, Japan, China, Russia, the United States, India and South Korea) agreed to contribute pieces of the reactor, with the central Iter organization attempting to coordinate. A review criticized Iter’s management for delays and cost overruns. Iter officials, however, say they are fixing the problems.

“This is a risk we consider well managed,” said Carlos Alejaldre, an Iter deputy director general.

General Atomics, a company in San Diego, is responsible for a main piece of the American contribution, a stack of huge magnetic coils at the center of Iter that will help control the shape of the hydrogen gas within the doughnut-shaped ring. The company has spent the past few years rounding up the machinery it will need to produce the seven coils, each more than 13 feet wide and weighing 120 tons. It will begin manufacturing a test coil this summer, and company officials say they are on track to finish production on schedule.

If Iter succeeds, a demonstration fusion power plant is to follow.

Tony S. Taylor, General Atomics’s vice president for magnetic fusion energy, started there in 1979. “I wanted to do something that was useful for the future of mankind,” he said. Back then, practical fusion power was expected to be 30 years away.

Thirty-five years later, Dr. Taylor, nearing retirement age, is still waiting. “It could have happened on that time scale,” he said. “What’s limiting our progress is funding.”

For most of his Livermore career, Dr. Hurricane worked in the classified shadows as a nuclear weapons designer. In 2009, he received a prestigious award for solving a mystery first recognized in the 1960s involving the physics of what happens inside nuclear bombs, although he still cannot say much about that.

“There was a discrepancy there,” he said, carefully choosing words. It was not a limitation of computer simulations but something more fundamental. “It was more mysterious,” he said. “We actually did resolve what the discrepancy was and understand the origin of the problem..”

With NIF’s failure at ignition, Dr. Hurricane was asked to take a fresh look. “The managers knew I just like solving problems,” he said. “And I don’t have any other ambition,” he joked.

In the rush to achieve ignition, the NIF scientists had used laser pulses that hit the fuel pellet as hard as possible, but the pellet was being ripped apart before fusion occurred. Dr. Hurricane adjusted the laser pulse to warm the gold cylinder initially. That reduced the implosion pressure, but calmed some of the instabilities, yielding a higher rate of fusion.

In September, Dr. Hurricane’s team had its first shot that showed signs of the fusion reaction spreading through the fuel.

“Now we at least have a sparking match,” said Jeff Wisoff, NIF’s acting director.

Since then, they have nudged up the energy by using cylinders of depleted uranium instead of gold, although the output is still considerably short of ignition.

But Dr. Hurricane is not aiming to solve the world’s energy problems.

“I actually don’t constrain myself personally with the practical applications at this point,” he said. “We don’t have to get a home run here.” In his baseball analogy, he said, he was looking to just get on base with singles and walks, and if enough small things work, then perhaps NIF will get to ignition.

Even then, practical fusion would still likely be decades away. NIF, at its quickest, fires once every few hours. The targets take weeks to build with artisan precision. A commercial laser fusion power plant would probably have to vaporize fuel pellets at a rate of 10 per second.

And if Dr. Bodner is right, the best approach is not even being pursued.

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