Computational challenges in magnetic-confinement fusion physics

Abstract

Magnetic-fusion plasmas are complex self-organized systems with an extremely wide range of spatial and temporal scales, from the electron-orbit scales (10−11 s, 10−5 m) to the diffusion time of electrical current through the plasma (102 s) and the distance along the magnetic field between two solid surfaces in the region that determines the plasma–wall interactions (100 m). The description of the individual phenomena and of the nonlinear coupling between them involves a hierarchy of models, which, when applied to realistic configurations, require the most advanced numerical techniques and algorithms and the use of state-of-the-art high-performance computers. The common thread of such models resides in the fact that the plasma components are at the same time sources of electromagnetic fields, via the charge and current densities that they generate, and subject to the action of electromagnetic fields. This leads to a wide variety of plasma modes of oscillations that resonate with the particle or fluid motion and makes the plasma dynamics much richer than that of conventional, neutral fluids.

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Figure 1: Magnetic-field structure in a tokamak.
Figure 2: Tokamak β-value limits.
Figure 3: Simulating ion cyclotron-resonance heating.
Figure 4: Gyrokinetic simulation of ITER plasmas.
Figure 5: Edge-region plasma simulation.
Figure 6: Contours of the density distribution of neutral-beam-injected ions obtained from simulating their trajectories in the equilibrium magnetic field.

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Acknowledgements

The authors wish to thank T.-M. Tran for his long-lasting support on HPC matters, and J. Faustin, D. Pfefferlé and F. Rive for help with the figure preparation.

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Correspondence to A. Fasoli.

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Fasoli, A., Brunner, S., Cooper, W. et al. Computational challenges in magnetic-confinement fusion physics. Nature Phys 12, 411–423 (2016). https://doi.org/10.1038/nphys3744

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