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World's Most Powerful Laser Could Pew Pew Its Way to Fusion Power

By Richard Adhikari
Jul 17, 2012 1:40 PM PT

The United States National Ignition Facility at Lawrence Livermore National Laboratory (LLNL) has successfully fired the most powerful laser beam ever recorded.

World's Most Powerful Laser Could Pew Pew Its Way to Fusion Power

It took 192 laser beams to deliver more than 500 trillion watts, or terawatts (TW), of peak power and 1.85 megajoules (MJ) of ultraviolet laser light to a target 2mm in diameter.

This is "1,000 times more power than the United States uses at any instant in time, and 1.85 megajoules of energy is about 100 times what any other laser regularly produces today," Breanna Bishop, an LLNL spokesperson, told TechNewsWorld.

The NIF project is part of a four-step process toward developing fusion energy as an alternative to coal and oil in the Laser Inertial Fusion Energy (LIFE) project, which is funded by the U.S. Department of Energy.

The idea is to have commercial LIFE plants on the U.S. national grid by the late 2020s. They will produce a self-renewing source of energy.

Move Over, Cyclops

The NIF's 192 lasers fired within a few trillionths of a second of each other. The beam-to-beam uniformity was within 1 percent, which makes the laser the most precise and reproducible to date.

This is the third time the laser has exceeded 1.8 MJ of total energy output since March. LLNL researchers worked closely with industry to develop optical equipment that could handle and produce these levels of extreme laser performance and developed in-house procedures to remove and mitigate the slight damage caused by firing the laser repeatedly.

"This was a very brief pulse, less than a trillionth of a second, so it was high intensity, but a small amount of power -- divide by 1 over 1 followed by 12 zeroes," Daniel Kammen, a distinguished professor of energy at the University of California at Berkeley, told TechNewsWorld.

How NIF Works

NIF pulls electricity off the power grid, stores it over a period of 60 seconds in banks of high-voltage capacitors then releases the energy through the lasers in a 400-microsecond burst, LLNL's Bishop said.

The released energy is largely captured to run the turbines and there is little wasted heat as this is a fusion reactor, UC Berkeley's Kammen said.

An IFE power plant consists of a target production facility, target injection and tracking systems, the laser, a fusion chamber, and a power combustion system.

In the plant, 10 to 20 pulses of fusion energy per second will heat a low-activation coolant such as lithium-bearing liquid metals or molten salts that surround the fusion targets. The coolant transfers the fusion heat to a turbine and generator to produce electricity. A laser of the scale of the NIF operating at this rate would produce more than 1,000 MW of electricity for the grid.

The plant needs to gain between 50 and 100 times as much energy as is generated by a laser shot if it is to be self-sustaining, as part of the electricity generated has to be recirculated to operate the laser.

Currently, the NIF laser operates at only a few shots a day because the researchers need to configure the experiments and let the facility's optical components cool down between shots. Operating an IFE plant at high pulse repetition rates will require adopting new technologies.

"NIF was built using technology from the 1990s," LLNL's Bishop pointed out. "Due to advances in technology in the years since, a commercial power plant would be much smaller. The target chamber would stay roughly the same size, but the building itself would be approximately half the size of the NIF. This facility would not need to be situated near running water such as a river, lake or sea."

Smaller Is Not Better

The NIF cost about US$3.5 billion dollars to build, LLNL's Bishop said. It's not currently known how much a similar plant for commercial use would cost to build in the mid-2020s.

The Ohio State University Department of Physics has built a laser that has a peak output of 400 TW, with a grant of just $6 million from the DoE. Called "SCARLET," it can fire once a minute.

Why can't the NIF build something that cheaply? LIFE is "based on lasers that use technology similar to ours, [but] the laser beams used in LIFE last millions of times longer than our laser pulses, so you require a vast amount of energy," Douglass Schumacher, an associate professor of physics at Ohio State, told TechNewsWorld.

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