editorial The way ahead for fusion As the construction of the ITER tokamak enters its next phase — the machine assembly — now is a good time for a recap of the history and current status of nuclear fusion research.

ometimes small changes can have a the last major component to be installed big effect. When Ernest Rutherford, before the cryostat will be closed up in late SMarcus Oliphant and Paul Harteck 2024, followed by a period of integrated carried out experiments in 1934, they were commissioning and testing to prepare for “surprised to find that on bombarding First Plasma. heavy hydrogen with diplons [deuterons] Of course, these milestones might an enormous effect was produced”1, require some adjustment due to the ongoing whereas in previous studies with alpha COVID-19 pandemic: work on site has particles impinging on a target, been reduced to critical activities with no significant effect had been observed. precautionary safety measures in place and Besides the discovery of and lockdown measures such as the temporary helium-3, their experiment achieved the first closures of workshops or factories in fusion reactions in the laboratory — fusion Credit: ITER Organization individual member states might affect the research took off with a bang. delivery of critical components. A report Among the first concepts of magnetic on the impact is expected this month, confinement fusion devices were the construction in the South of France, around but Bernard Bigot believes this not to be a stellarator (with its helically twisted plasma twenty years should pass. major setback. shape), proposed by the American physicist Problems with the design and manage­ The strong performance and vigorous , and the tokamak (which ment issues delayed the start of operations pace of progress demonstrated by the confines the plasma in the form of a donut), and led to a substantially revised budget of ITER Organization in reaching critical introduced by Soviet scientists Andrei roughly €20 billion. However, following the milestones of the new baseline has also Sakharov and Igor Tamm. Another approach arrival of Director-General Bernard Bigot shifted public perception. The conversation (inertial confinement fusion), put forward in 2015, a root and branch review of the is now less cynical compared to the first, by John Nuckolls and colleagues, implodes project led to a new baseline design. This rather troubled, years of the project — with capsules filled with heavy hydrogen isotopes revised schedule marked a turning point for the growing public awareness that the using high-energy beams2. the construction of ITER: the first hydrogen issue of climate change becomes ever more Today’s fusion community actively plasma discharge is expected in 2025, and urgent. After First Plasma, installation of explores all these paths — alongside other the work to achieve this is 70% complete critical components for deuterium–tritium concepts — as we highlighted in a special and therefore on track. We spoke to Bernard operation such as additional heating Insight issue back in 20163. In September Bigot and Tim Luce, head of ITER’s Science or a fuel recycling system will prepare 2019, the Nature Conference “Advances and & Operations Department, about the status the machine for its ultimate goal: the Applications in Plasma Physics” not only of the project. You can read the conversation demonstration of the feasibility of fusion brought together scientists working on elsewhere in this issue. power is expected to commence in 2035. different fusion concepts but also connected The progress is most strikingly visible at This seems like a long way down the road, the wider plasma physics community — from the ITER worksite in St. Paul-lez-Durance, but ITER’s recent track record is impressive. astrophysical plasmas to laser–plasma France. Earlier this year, the tokamak Although ITER will not be the immediate interactions, cold/dusty plasmas and building was handed over to the ITER solution to the problem of clean and applications. In the sessions dedicated Organization and the 1,250-tonne cryostat affordable energy, it will be crucial in to magnetic confinement fusion, the base was installed within the required informing the design of the next generation ambivalence of the audience was tangible: precision of only 3 mm. With the first major of fusion reactors that will produce will the ITER tokamak (which is Latin components, such as toroidal or poloidal electricity instead of heat. Scientists are for ‘the way’) live up to expectations and magnetic field coils, also arriving on site, the thinking way ahead: conceptual designs demonstrate the feasibility of nuclear focus has now shifted from the construction for commercial tokamaks as a globally ? of the infrastructure to machine assembly, a distributable, sustainable supply of energy Large-scale international projects milestone that was celebrated on 28 July. are already underway. This is the way come into existence on the timescale of The next milestones include the towards a future with safe and sustainable decades rather than years, and ITER is no commissioning of the liquid helium energy. ❐ exception. As Matteo Barbarino recounts cryogenic plant and the pre-assembly of in a Comment on the history of nuclear the (nine) vacuum vessel sectors with Published online: 28 August 2020 fusion, the ITER collaboration was founded two toroidal magnetic field coils each and https://doi.org/10.1038/s41567-020-01043-9 more than thirty years ago by the European thermal shielding, with the first module References Union (through the Euratom treaty), Japan, expected to be installed towards the end of 1. Oliphant, M. L. E., Harteck, P. & Rutherford, E. Proc. R. Soc. A the Soviet Union and the United States, who the year. In addition, the first of six magnets 144, 692–703 (1934). were later joined by the People’s Republic making up the central solenoid is expected 2. Nuckolls, J., Wood, L., Tiessen, A. & Zimmerman, G. Nature 239, 139–142 (1972). of China, the Republic of Korea and India. to be shipped from the United States to 3. Insight: nuclear fusion. Nat. Phys. https://www.nature.com/ From the initial proposal to the start of France later this year. The solenoid will be collections/bccqhmkbyw/ (2016).

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