The hopes of fusion researchers worldwide are pinned to the fortunes of the National Ignition Facility (NIF), a $3.5 billion laser center at Lawrence Livermore National Laboratory in California, which is trying to show that it is possible to create a self-sustaining fusion reaction that could serve as a source of energy. But a change in its milestones, revealed in an internal NIF document Science has seen, has highlighted the concerns of some in the field that the path NIF researchers have taken may not be the right one. Funded by the U.S. Department of Energy (DOE), NIF aims to use a huge laser, the highest energy laser in the world, to crush a tiny fuel capsule to temperatures and pressures higher than in the center of the sun. The goal is to spark a fusion fire in the center of the fuel to start it burning. But the fuel is not considered ignited until high-energy alpha particles produced by the fusion burn heat the surrounding fuel enough to keep the burn going until a significant fraction of the fuel is used.
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