LIVERMORE, Calif. -- In the dark early morning hours, scientists conduct an almost daily ritual out here at the National Ignition Facility at Lawrence Livermore National Laboratory: a countdown. In a NASA-style control room, researchers and technicians huddle around LCD monitors on semicircular desks facing a wall of five projection screens.
The countdown reaches zero, the world's most powerful laser fires silently for a fraction of a second at a fuel target, and results pour in. The equipment winds down, and scientists spend the next day poring over numbers, checking instruments and preparing for the next shot.
"In some ways, it's the most disappointing end of a countdown because you don't see something blasting off into the sky," said Mike Dunne, director of laser fusion energy at NIF. "You wait a few hours to get the data, and then it becomes exciting again."
Though it is a bit anticlimactic compared to a rocket launch, scientists here are nevertheless aiming for the stars with every attempt at ignition.
Specifically, they want to harness fusion, the reaction that fuels the sun and other stars. Outside the main entrance of the facility, a building resembling a warehouse spanning more than three football fields, a banner cheerfully exclaims, "Bringing Star Power to Earth."
Our sun turns 600 million tons of hydrogen into helium every second, creating the heat and light that bathe our planet 93 million miles away, driving air currents, feeding plants and tanning skin. Bottling and channeling even a minuscule fraction of that energy here on Earth would radically change the world's economy and humanity's footprint on the environment.
"It just suffers from the one small problem that nobody's ever shown it to work," Dunne explained.
The long road to ignition
While the hydrogen bomb program proved man could liberate fusion energy, harnessing it for peaceful purposes has been a struggle since the 1940s. Researchers have overcome challenges only to see new ones present themselves. Now, with tight funds, waning public patience and an increasingly urgent need for solutions to climate change, fusion research faces uncomfortable questions of which direction to go, how to get there and what gets left behind.
In the United States, government-funded labs are simultaneously pushing two tracks -- inertial fusion and magnetic confinement fusion -- but neither with the vigor needed to advance the field meaningfully, according to scientists. Though researchers on both sides tout their accelerating progress, neither has achieved ignition, the threshold where the reaction gives off more energy than is needed to start it.
Think of a campfire. A lone spark might not be enough to start a roaring flame, but lighting some tinder could bring the logs alight. At this stage, scientists are still using too much tinder and not burning enough of the wood to make a campfire worthwhile.
However, for the most part, they understand the physics behind fusion. In particular, researchers want to fuse two hydrogen isotopes. The hydrogen we know and love, also called protium, is simply one proton encircled with one electron. Stick a neutron onto that proton and you have deuterium, which is naturally present in seawater in concentrations of roughly one part per 6,000. Add two neutrons and you have tritium, which is rare since it has a half-life of only 12.3 years.
In a fusion reaction, you want to get one deuterium to stick to one tritium, forming a helium nucleus of two protons and two neutrons. In the process, the reaction kicks off the extra neutron, which can fly off to boil water or another heat transfer fluid.
It also turns out that the newly formed helium nucleus is less massive than the sum of its parts. The difference in mass dissipates as energy governed by Einstein's famous formula, E=mc², where the energy equals the mass times the square of the speed of light. This means a very tiny amount of stuff can yield a huge amount of energy to propagate the fusion reaction.
When the head of the Atomic Energy Commission at the time, Lewis Strauss, infamously quipped in 1954 that electricity would become "too cheap to meter," he was likely referring to nuclear fusion, not nuclear fission, the atom-splitting reaction that powers conventional nuclear power plants today.
Dunne observed that 1 gram of fusion fuel would fulfill the energy needs of an American for a year.
But at the atomic level, opposites attract and like charges repel. Getting positively charged nuclei to overcome their aversion to each other requires a huge energy input -- like very high temperatures to increase the likelihood that these atoms will collide or immense compression to force them to stick together.
In nature, this happens in stars, where their immense gravity brings nuclei together to form heavier elements. On Earth, it has happened in H-bomb tests.
For fusion-powered energy, you need big science -- massive laboratories, hundreds of researchers making this their life's work, advanced equipment and a concerted multiyear drive -- and NIF is nothing if not big science.
Firing up the lasers
When researchers attempt ignition, a bank of capacitors charges up and triggers a flash of light at the master oscillator that generates 192 laser beams. The beams split, bend, twist, bounce and amplify as they travel 1,500 meters through the facility, modulated through 60,000 control points in five-millionths of a second.
"If you saw the recent 'Star Trek' movie, this is where they loaded the photon torpedoes," Dunne said, presenting the switchyard, the part of the building that routes lasers to their respective paths.
Two million joules of ultraviolet laser energy then converges on a cylindrical target called a hohlraum, after the German word for "cavity." Inside is a tiny pellet of deuterium and tritium. The goal here is to compress the sphere to trigger fusion without it deforming or extruding, a vexing challenge for engineers who are trying to improve their yields with computer simulations along with trial and error.
Scientists at NIF recently hinted that they have managed to get more energy out of the fuel than the energy hitting it. This is a major achievement, but because of inefficiencies and losses, this is still far short of the energy used to generate the light, which is the ignition threshold (ClimateWire, Oct. 15).
The other main alternative is magnetic confinement. Since the operating temperature for fusion is in the hundreds of millions degrees Celsius, hotter than any known material can withstand, engineers found they could contain a plasma -- a neutral electrically conductive, high-energy state of matter -- at these temperatures using magnetic fields.
The most common method to do this is with powerful magnets around a container in the shape of a torus, akin to a doughnut, called a tokamak. At the Princeton Plasma Physics Laboratory, engineers are currently upgrading the National Spherical Torus Experiment, the main fusion project at the lab.
"Fusion has an amazing set of properties when it becomes commercializable," said Stewart Prager, director of the plasma lab. The reaction produces zero emissions and doesn't explode or trigger runaway events. Since it draws half its fuel from seawater, there is enough to last humanity millions of years.
The goal for magnetic fusion is to generate roughly 10 times as much energy as is needed to contain the plasma. "We've come an enormous distance," Prager said. "We're ready to shift from being a science-based program to really being an energy-based program."
This will manifest in the International Thermonuclear Experimental Reactor, the world's largest tokamak, under construction in France. "We sometimes say ITER will be the first burning plasma experiment," Prager said.
'Not at the point of picking a winner'
Michel Claessens, head of communications at ITER, echoed Prager. "We're not starting from scratch; simply ITER will be the biggest one," Claessens said. "The aim is to show the technical feasibility of fusion energy."
The project emerged from a meeting between President Reagan and the Soviet Union's general secretary, Mikhail Gorbachev, in 1985 to develop fusion power, with the premise that no nation can face the world's energy challenges alone. The European Union and several other governments are contributing cash, equipment and resources to the endeavor, which may end up costing more than €13 billion ($17.6 billion).
"Because the contributions are in kind and members are not obliged to tell us what it cost them, we will never have a detailed cost of ITER," Claessens said, adding that participants will likely have to wait until 2027 before they figure out for certain whether this is a game-changing energy source or just the most expensive way to boil water ever built.
NIF also has a commercial generator in the pipeline, the Laser Inertial Fusion Energy plant. Instead of using water to transfer heat, the plant uses lithium. When struck with a neutron, it produces tritium, the part of the fuel you can't get from the ocean.
According to Dunne, it will operate more like an internal combustion engine than a reactor: injecting the fuel, compressing it, igniting it and exhausting the detritus.
Though inertial and magnetic fusion scientists have a bit of a rivalry, Prager said both deserve support. "The need to have solutions to climate change is so severe that we want to pursue all promising approaches," he said. "We're not at the point of picking a winner. They should both be pursued, I would say."
Even as researchers at NIF inch toward higher energy yields every night, outside, another fusion reactor crests every morning between the wind turbines on the hills surrounding Livermore Valley, taunting them over the horizon. As close as they think they are to ignition, the sun has a 4.5-billion-year head start.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
