One giant leap for clean energy

Scientists have long dreamed of nuclear fusion, a way to power the planet without risk or emissions. Breakthroughs have been scarce - until now

- Arthur Turrell

A laser-initiated experi-ment at the United States National Ignition Facility, based at Lawrence Livermore National Laboratory in California, made a significant breakthrough on 8 August in reproducing the power source of the stars, smashing its own 2018 record for energy released from nuclear fusion reactions 23 times over.

The nuclear energy that was released was equal to 70% of the laser energy used to create the reaction. A pulse of light, focused to tiny spots within a vacuum chamber, triggered the collapse of a capsule of fuel from roughly the size of the pupil in your eye to the diameter of a human hair. This implosion created the extreme conditions of temperature and pressure needed for atoms of hydrogen to combine into new atoms and release, kilogram for kilogram, 10m times the energy that would result from burning coal.

The energy generated by the NIF is only just enough to boil a kettle. Despite this, it is nevertheless a landmark moment. The result is tantalisingly close to a demonstration of “net energy gain”, the long-sought-after goal of fusion scientists in which an amount greater than 100% of the energy put into a fusion experiment comes out as nuclear energy. The aim of these experiments is to show proof of principle: that energy can be generated. The team behind the success are close to achieving this: they have managed a more than 1,000-fold improvement in energy release since 2011. Prof Jeremy Chittenden, the co-director of the Centre for Inertial Fusion Studies at Imperial College London, said last month: “The pace of improvement in energy output has been rapid, suggesting we may soon reach more energy milestones, such as exceeding the energy input from the lasers used to kick start the process.”