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arXiv · 2109.03427

Energy-selective confinement of fusion-born alpha particles during internal relaxations in a tokamak plasma

Andreas Bierwage·Kouji Shinohara·Yevgen Kazakov·Vasili Kiptily·Philipp Lauber·Massimo Nocente·Žiga Štancar·Shuhei Sumida·Masatoshi Yagi·Jeronimo Garcia·Shunsuke Ide·JET Contributors
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Abstract

Long-pulse operation of a self-sustained fusion reactor using toroidal magnetic containment requires control over the content of alpha particles produced by D-T fusion reactions. On the one hand, MeV-class alpha particles must stay confined to heat the plasma. On the other hand, decelerated helium ash must be expelled before diluting the fusion fuel. Our kinetic-magnetohydrodynamic hybrid simulations of a large tokamak plasma confirm the existence of a parameter window where such energy-selective confinement can be accomplished by exploiting internal relaxation events known as `sawtooth crashes'. The physical picture -- consisting of a synergy between magnetic geometry, optimal crash duration and rapid particle motion -- is completed by clarifying the role played by magnetic drifts. Besides causing asymmetry between co- and counter-going particle populations, magnetic drifts determine the size of the confinement window by dictating where and how much `reconnection' occurs in particle orbit topology.

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Andreas Bierwage, Kouji Shinohara, Yevgen Kazakov, Vasili Kiptily, Philipp Lauber, Massimo Nocente, Žiga Štancar, Shuhei Sumida, Masatoshi Yagi, Jeronimo Garcia, Shunsuke Ide, JET Contributors. 2021-09-08. Energy-selective confinement of fusion-born alpha particles during internal relaxations in a tokamak plasma. https://doi.org/10.1038/s41467-022-31589-6

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