The main purpose of the National Ignition Facility is to conduct experiments to help the United States maintain its nuclear weapons. When operations began in 2009, however, the facility hardly generated any fusion at all, an embarrassing disappointment after a $3.5 billion investment from the federal government. The successful experiment finally delivers the ignition goal that was promised when construction of the National Ignition Facility started in 1997. “You see one diagnostic and you think maybe that’s not real and then you start to see more and more diagnostics rolling in, pointing to the same thing,” said Annie Kritcher, a physicist at Livermore who described reviewing the data after the experiment. This crossed the threshold that laser fusion scientists call ignition, the dividing line where the energy generated by fusion equals the energy of the incoming lasers that start the reaction. Out flowed a flood of neutron particles - the product of fusion - which carried about 3 megajoules of energy, a factor of 1.5 in energy gain.
In a brief moment lasting less than 100 trillionths of a second, 2.05 megajoules of energy - roughly the equivalent of a pound of TNT - bombarded the hydrogen pellet. That generated an inward onslaught of X-rays that compresses a BB-size fuel pellet of deuterium and tritium, the heavier forms of hydrogen. The laser beams entered at the top and bottom of the cylinder, vaporizing it. 5 when 192 giant lasers at the laboratory’s National Ignition Facility blasted a small cylinder about the size of a pencil eraser that contained a frozen nubbin of hydrogen encased in diamond. In all of the efforts by scientists to control the unruly power of fusion, their experiments consumed more energy than the fusion reactions generated. There was always a nagging caveat, however. In experimental reactors and laser labs on Earth, fusion lives up to its reputation as a very clean energy source. Within the sun and stars, fusion continually combines hydrogen atoms into helium, producing sunlight and warmth that bathes the planets. If fusion can be deployed on a large scale, it would offer an energy source devoid of the pollution and greenhouse gases caused by the burning of fossil fuels and the dangerous long-lived radioactive waste created by current nuclear power plants, which use the splitting of uranium to produce energy.
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