Energy-selective conﬁnement of fusion-born alpha particles during internal relaxations in a tokamak plasma
Professor Kouji Shinohara of the Department of Complexity Science and Engineering in the Graduate School of Frontier Sciences played a leading role in the research project.
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. Here, we report results of kinetic-magnetohydrodynamic hybrid simulations of a large tokamak plasma that 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 -- a synergy between magnetic geometry, optimal crash duration and rapid particle motion -- is completed by clarifying the role of 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.
Title: Energy-selective confinement of fusion-born alpha particles during internal relaxations in a tokamak plasma
Authors: A. Bierwage, K. Shinohara, Ye.O. Kazakov, V. G. Kiptily, Ph. Lauber, M. Nocente, Ž. Štancar, S. Sumida, M. Yagi, J. Garcia, S. Ide & JET Contributors
Title: Nature Communications
Date: 08 July 2022