Efforts to develop fusion as a viable alternative energy source continue but progress has been slow. In the context of inertial confinement fusion, in which a fuel target is compressed and heated to initiate nuclear fusion, a key experimental goal is to reach a stage where the amount of energy deposited into the fuel during the compression/heating process is exceeded by the amount of energy generated by the induced fusion reactions. This threshold — the attainment of a 'fuel gain' that is greater than one — has now been reached at the National Ignition Facility in Livermore, California. They used 192 laser beams to heat and compress a fuel pellet to the point at which nuclear fusion reactions take place and obtained a yield 10 times greater than previously achieved. Further advances will be required, however, before the fusion energy yield exceeds the total energy required to compress the fuel pellet.
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