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.