For the first time on Earth, a controlled fusion reaction has generated more power than it requires to run, researchers have confirmed. The experiment is a major milestone towards commercial fusion power but experts say there is still a vast engineering effort needed to increase efficiency and reduce cost.
Rumours of the experiment at Lawrence Livermore National Laboratory (LLNL) in California emerged on 11 December, but the news has been formally announced a press conference today. In an experiment on 5 December the lab’s National Ignition Facility (NIF) fusion reactor generated a power output of 3.15 megajoules from a laser power output of 2.05 megajoules – a gain of around 150 per cent.
There are two main research approaches aiming to achieve viable nuclear fusion. One uses magnetic fields to contain a plasma, and the other uses lasers. NIF uses this latter approach, known as inertial confinement fusion (ICF), where a tiny capsule containing hydrogen fuel is blasted with lasers, causing it to heat up and rapidly expand. This creates an equal and opposite reaction inwards, compressing the fuel. The nuclei of hydrogen atoms fuse together to form heavier elements, and some of their mass is released as energy – just as it is in the sun.
Until now, all fusion experiments have required more energy input than they generate. NIF’s previous record, confirmed in August this year, produced an output that was equivalent to 72 per cent of the energy input from its lasers. Today’s announcement confirms that researchers have not only reached the crucial break-even milestone, but surpassed it – albeit if you ignore the energy required to power the lasers in the first place, which is much higher than the output from the fusion reaction.
The White House Office of Science and Technology’s policy director Arati Prabhakar said it was a “tremendous example of what perseverance can achieve” and that the results brings viable fusion power one step closer.
“It took not just one generation but generations of people pursuing this goal. This duality of advancing the research, building the complex engineering systems, both sides learning from each other – this is how we do really big hard things, so this is just a beautiful example,” she said.
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