Scientists in the US have announced a major breakthrough in the race to harness nuclear fusion, which could eventually provide ‘nearly limitless’ clean energy.
Researchers from the National Ignition Facility at the Lawrence Livermore National Laboratory (LLNL) in California said that they had succeeded in generating more energy than they put into a fusion experiment – a landmark achievement known as net energy gain.
LLNL director Dr Kim Budil called it a historic achievement made possible by thousands of people working on the endeavour over the past six decades.
Nuclear fusion is the process that occurs in stars, including our sun, and has been described as the ‘Holy Grail’ of clean energy.
It takes two light nuclei and merges them to form a single heavier nucleus, with energy being produced in the process.
Current nuclear energy production involves a process known as nuclear fission.
This is essentially the opposite of nuclear fusion, as it involves splitting heavy atoms apart.
Of the two approaches, fission is easier to achieve but fusion has the potential to produce much more energy while cutting out the greenhouse gases and long-term radioactive waste.
Experiment involved firing high-powered lasers at a gold cylinder
One of the main challenges of nuclear fusion has been that forcing the nuclei together and keeping them there requires working with very high pressures and temperatures.
Where fusion has been achieved, it has until now taken more energy being put in than the process has been able to put out.
The National Ignition Facility is a huge complex that cost $3.5bn (£2.85bn) to build.
It housed the recent experiment, which involved placing a tiny amount of hydrogen inside a capsule the size of a peppercorn.
This was then put inside a centimetre-long gold cylinder called a hohlraum, which was bombarded by up to 192 giant lasers.
The intense energy heated the temperature inside the cylinder to a temperature hotter than the sun’s surface, bathing the fuel pellet in x-rays.
The extremes of temperature and pressure – usually found only inside stars – fused the hydrogen nuclei, resulting in 2.05 megajoules (MJ) of laser energy going in and around 3.15MJ coming out.
There’s a long way to go before nuclear fusion powers homes and industry, but this still represents a hugely important tipping point and a proof of concept.
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