At the Heart of the Atom

Did Physicists Recognize the Military Uses of Fission?

How would lasers produce fusion?

The second method of producing fusion is called inertial confinement. Tiny glass, plastic, or metallic spheres containing about 10 milligrams of deuterium-tritium fuel mixture at high pressure are bombarded on all sides by extremely powerful lasers. The lasers vaporize the sphere, driving a strong inward shock wave that compresses the fuel enough to create fusion.

The National Ignition Facility, located at Lawrence Livermore Laboratory in California, has been under construction since 1997. The design goal is to create a 2 mega-joule flash of ultraviolet energy that hits the target from 192 separate beamlets. All of the beamlets must strike the target within a few picoseconds. In January 2010 the laser beams delivered 700 kilojoules to a test sphere, heating the gas inside to 3.3 million kelvins. It takes hours for the lasers to cool enough to deliver another pulse. The engineering goal is to deliver one pulse each five hours. Before deuterium-tritium fusion fuel can be used neutron shields have to be built to protect the lasers. There are no accepted engineering plans to convert the energy released to electrical energy. One proposed method is to surround the bead with a blanket of liquefied lithium that would be further heated by the energy released.


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