The JET facility, in Culham, Oxfordshire, ended experiments in December of 2023. The reason why it’s still so important is that JET was not only a world leader in fusion experiments, but its legacy lives on. Fusion is the holy grail of producing clean energy and at this moment in time, is our only chance for mitigating climate change (there’s also fission, but that’s another article). At the end of its operating lifespan in September 2023, JET set the current fusion record, 69 megajoules of energy produced in a controlled reaction. This is the same amount of energy you would get from burning 2 kilograms of coal, but from using just 0.21 milligrams of fuel, which is utterly phenomenal. This was a breakthrough on British soil (though the project itself is an EU collaboration). It’s nice to know that the UK is in the limelight once more. 

 

JET stands for Joint European Torus (a torus is a doughnut shape) and has been operating since 1983. Nuclear Fusion is when two light nuclei of atoms are fused together to form one heavier nucleus, releasing huge amounts of energy in the process. Fusion can produce almost limitless amounts of clean, carbon-free energy, and the fuels for fusion are in easy supply. They are just isotopes of hydrogen, which is the most abundant element in the universe.

 

JET achieved fusion by heating the fuels by hundreds of millions of degrees (much hotter than the Sun) to make them electrically charged gases called plasmas. Whilst the fusion reaction would take place, the plasmas would be contained using magnetic fields in the shape of a doughnut, hence the name ‘torus’. Another way to achieve fusion is to strike a pellet of fuel at all sides with lasers, making it implode and fuse the fuels. This method achieves fusion with extremely high pressures, rather than extremely high temperatures like in JET. This is used in the National Ignition Facility (NIF) in the USA. However, NIF’s record for fusion energy produced is 20 times less than JET’s, and so most fusion reactors planned will  achieve fusion in the same way as JET.

 

So what’s the next step after JET? ITER (pronounced ‘eater’, because why wouldn’t you?) is currently being constructed in the south of France and should be completed in 2025. Essentially, ITER (International Thermonuclear Experimental Reactor) is a much larger version of JET (73 to 12 metres high), which should allow it to reach greater temperatures, close to what we would want for a commercial fusion reactor connected to the National Grid. Meanwhile, our government is leapfrogging the ITER step, and is currently in the process of planning the design for a fusion energy plant. This is known as STEP (Spherical Tokomak for Energy Production) and should be completed in the 2040s. The full fusion dream is near!

 

Curious for more? The Culham facility, where JET is based, regularly opens its doors for visitors to visit this historic fusion centre. Or watch Star Makers- The Energy of Tomorrow, a behind-the-scenes film about life working at JET, available on Prime Video.