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.
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 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 frozen deuterium 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.
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Source: nytimes.com by Kenneth Chang