Nuclear fusion, the ‘holy grail’ of energy, has long eluded scientists. In a fusion reaction, hydrogen plasma fuses to become helium under enormous heat and pressure, and releases huge amounts of clean, renewable energy in the process. However, this virtually limitless source of energy faces technical challenges that have thus far been insurmountable.
Scientists have said for decades that generating power from nuclear fusion is only a few decades away – this time, could it be true? Take a look inside the fusion reactors around the world that are bringing us closer to achieving the dream.
Alcator C-mod reactor, MIT Plasma Science and Fusion Center, USA
![Inside the doughnut-shaped vacuum chamber of the Alcator C-mod reactor at MIT Plasma Science and Fusion Center © Bob Mumgaard/Creative Commons A cylindrical column plated in metal inside a doughnut-shaped chamber. A person in a full-body white suit is inside the chamber © Bob Mumgaard/Creative Commons](https://c02.purpledshub.com/uploads/sites/41/2021/11/crop_Fport_inwards_panosphere_Man-crop-cee8541.jpg?webp=1&w=1200)
Experimental Advanced Superconducting Tokamak (EAST) reactor, China
![The team at China’s EAST reactor inspect and adjust the device ahead of its record-breaking demonstration in June 2021 © Shutterstock The team at China’s EAST reactor inspect and adjust the device ahead of its record-breaking demonstration in June 2021 © Shutterstock](https://c02.purpledshub.com/uploads/sites/41/2021/11/shutterstock_editorial_11977584k-crop-a276ebb.jpg?webp=1&w=1200)
![China’s EAST reactor managed to maintain plasma at 120,000,000°C for 101 seconds in June © Shutterstock China's EAST reactor © Shutterstock](https://c02.purpledshub.com/uploads/sites/41/2021/11/shutterstock_editorial_11977588c-crop-6fdc11d.jpg?webp=1&w=1200)
National Spherical Torus Experiment (NSTX-U), Princeton Plasma Physics Laboratory, USA
![The NSTX-U reactor has been designed to create a spherical plasma, in contrast to the toroidal (doughnut-shaped) plasmas of other tokamaks © Elle Starkman/Princeton Plasma Physics Laboratory Two people working on the chamber inside the NSTX-U reactor © Elle Starkman/Princeton Plasma Physics Laboratory](https://c02.purpledshub.com/uploads/sites/41/2021/11/35573168676_72daeac1f1_o-crop-736889e.jpg?webp=1&w=1200)
International Thermonuclear Experimental Reactor, France
![35 nations have invested in the ITER, which is being built in France © ITER Organisation A view from above of ITER under construction © ITER Organisation](https://c02.purpledshub.com/uploads/sites/41/2021/11/pit_02-07-2021_small-crop-010145b.jpg?webp=1&w=1200)
![The doughnut-shaped chamber at the heart of ITER © ITER Organisation The doughnut-shaped chamber at the heart of ITER. It is a large metal construction © ITER Organisation](https://c02.purpledshub.com/uploads/sites/41/2021/11/vvs6_from_chang-hyun_1-crop-92008b6.jpg?webp=1&w=1200)
Joint European Torus reactor, UK
![The Joint European Torus (JET) reactor in the UK is working on deuterium-tritium fusion reactions intended to sustain higher power outputs for longer © EUROfusion Consortium Inside the chamber of the JET reactor © EUROfusion Consortium](https://c02.purpledshub.com/uploads/sites/41/2021/11/Euro_fusion_CP10j-343-18-crop-00623fd.jpg?webp=1&w=1200)
- This article first appeared inissue 369ofBBC Science Focus Magazine–find out how to subscribe here