Thursday, March 26, 2009

The World's Biggest "Death Star" Wannabe

This will be the world's biggest laser, a composition of 192 lasers meant to create nuclear fusion - an emulation of the sun - ... and it's running. It's all going down at the National Ignition Facility (NIF). If all goes according to plan - within two, maybe three years - mean streamin' beams will give birth to fusion reactions, that... churn out more energy than is required to create them. A dream of humankind.

Check into it (source):

The National Ignition Facility (NIF), at the U.S. Department of Energy's Lawrence Livermore National Laboratory (LLNL), comprises 192 lasers that fire imultaneously at precisely the same point in space: a sphere of fuel two millimeters in diameter. They are designed to deliver 1.8 megajoules of energy in a few billionths of a second. That's enough to compress the fuel to a speck 50 micrometers across and heat it up to three million degrees Celsius. The lasers, which were fired together for the first time last month, have so far produced pulses of 1.1 megajoules. "Depending on how you count it, it's between 60 and 100 times more energetic than any laser system that's ever been built," says Edward Moses, the principle associate director for NIF and Photon Science at LLNL. Eventually, the fusion reactions produced by each pulse are expected to generate at least 10 times the energy delivered by the lasers, a
significant net gain that could be useful for generating power.

The $3.5 billion facility, which has been in development for 15 years, was funded primarily as a way to better understand nuclear weapons, after a ban on testing in the 1990s. NIF will produce tiny thermonuclear explosions that give scientists insight into what happens when a nuclear bomb goes off. That data can, in turn, be used to verify computer simulations that help determine whether the United States' nuclear stockpile will continue to work as the weapons age. The data could also provide insight into the processes that power the sun and other stars, and answer other scientific questions. Finally, NIF could serve as a proof-of-concept design for a fusion power plant.

To generate fusion, 192 laser beams are generated, amplified, converted from infrared to ultraviolet light, and then aimed at a small gold canister the size of a pencil eraser. Inside that canister is a sphere containing the fuel: two isotopes of hydrogen called deuterium and tritium. The lasers are positioned all around the sphere to create the temperatures and pressures needed to ignite a fusion reaction. If all goes as planned, some of the hydrogen atoms should fuse, producing helium and releasing energy. This should, in turn, cause more fusion reactions until the fuel runs out. The whole process will take just a few billionths of a second.


The current facility isn't built to generate electricity. But Moses says that with the right funding, a power plant using fusion from a system like the one at NIF could be running in a decade. In contrast, power plants based on the Z machine at Sandia or the ITER system in France are decades away.

Other experts, however, are more skeptical. "If NIF is successfully, they'll still be a very long way from turning this into a practical energy source," says Ian Hutchinson, professor and head of nuclear science and engineering at MIT. For example, he says, a power plant would require the lasers to fire much more frequently than the NIF lasers--5 to 10 times a second, rather than once every couple of days, as is possible now. (Each burst would release energy equivalent to about five kilowatt-hours of electricity: by comparison, an average nuclear power plant generates 12.4 billion kilowatt hours a year, while an average house requires about 1,000 kilowatt-hours per month.)

In contrast, ITER will use magnetic confinement of hot plasma to produce fusion, a system that produces a continuous stream of energy that could be more suited to generating electricity than the very short bursts of energy produced by NIF, he says.


- Brewskie

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