The tokamak is the most advanced approach to fusion and is approaching operation under power-plant conditions, promising sustainable, low-emission, baseload power to the grid. As the heating power of a tokamak is increased above a threshold, the plasma suddenly bifurcates to a state of high confinement, creating a region of plasma with a large pressure gradient at its edge. This bifurcation results in a repetitive sequence of explosive filamentary plasma eruptions called edge-localized modes (ELMs). ELMs on next-step tokamaks, such as ITER, will likely cause excessive erosion to plasma-facing components and must be controlled. We present what is understood about how ELMs form, their filamentary nature and the mechanisms that transport heat and particles to the first wall of the tokamak. We also discuss methods to control ELMs, including magnetic perturbations.
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The authors gratefully acknowledge the comments on this manuscript given by Samuli Saarelma, William Morris and Jack Connor. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement no. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work has been part-funded by the RCUK Energy Programme (grant number EP/P012450/1). To obtain further information on the data and models underlying this paper, please contact PublicationsManager@ukaea.uk. Simulations published in this review have benefited from the support of EUROfusion on the Marconi HPC cluster (CINECA, Italy), as well as the support of PRACE on the MareNostrum HPC cluster (BSC, Spain).
The authors declare no competing interests.
Nature Reviews Physics thanks F. Jenko and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Ham, C., Kirk, A., Pamela, S. et al. Filamentary plasma eruptions and their control on the route to fusion energy. Nat Rev Phys 2, 159–167 (2020). https://doi.org/10.1038/s42254-019-0144-1