For well over a decade, physicists at the Lawrence Livermore National Laboratory in California have been attempting to do something in the lab that had only ever previously occurred inside the warheads of hydrogen bombs. Their aim has been to use intense pulses of light from the world’s biggest laser – the $3.5bn National Ignition Facility (NIF) – to crush tiny capsules of hydrogen fuel such that the exceptional temperatures and pressures created therein yield energy-producing fusion reactions. Until the end of last year, a series of technical setbacks had prevented them from reaching their goal, known as ignition. But just after 1 a.m. on 5 December a larger-than-usual burst of neutrons in the detectors surrounding the laser’s focus signalled success – the reactions in this case having produced more than 1.5 times the energy they consumed.

The feat created headlines around the world and stimulated the imagination of the public, politicians and fusion experts alike. US energy secretary Jennifer Granholm hailed the “landmark achievement”, while Michael Campbell of the University of Rochester in the US described the result as a “Wright Brothers moment” for fusion research. For Steven Rose of Imperial College London, the announcement removes any lingering doubt that such high fusion energies are attainable. “If you don’t get an energy gain greater than one, people might claim you can never achieve it,” he says.

The result renewed optimism that fusion might finally enable a new source of clean, safe, secure and sustainable energy. Now, governments and especially private companies are looking to exploit the huge potential of fusion energy – with some firms even promising that they will deliver electricity to the grid from pilot power plants by early in the next decade.

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