Speaker
Description
Abstract. The effect of highly energetic particles (EPs) needs to be well understood in future burning plasma experiments as they will provide a large fraction of the total pressure and can strongly interact with the thermal bulk plasma. In this contribution we describe numerical simulations of n=1 instabilities in tokamak plasmas like the internal kink and fishbone mode which is driven unstable by EPs. Fishbones can lead to the redistribution and loss of EPs but may also be beneficial for tokamak operation, as they are regularly present in discharges with improved confinement at AUG [1,2], JET [3], HL-2A [4] and DIII-D [5].
The nonlinear extended MHD code JOREK [6] and the global electromagnetic gyrokinetic code ORB5 [7] are run for similar simulation cases, to gain insights regarding the differences between the two models and the underlying physics processes. JOREK treats the bulk plasma as a fluid and evolves the MHD equilibrium self-consistently in time, taking into account the evolution of the EP distribution function. The fast ions are modeled with a particle-in-cell (PIC) technique. A full-f formulation and an anisotropic pressure coupling scheme to the fluid are used [8]. On the other hand, ORB5 describes not only the fast ions but also the electrons and thermal ions drift- or gyrokinetically. Similarly, a PIC method is used but with a delta-f formulation. Using a kinetic description for the electrons instead of a fluid model in contrast to previous work [5] demands special care during the simulation setup.
Linear properties from the simulation runs like growth rates and mode frequencies are compared and the nonlinear behavior like frequency chirping of the mode, mode saturation and the effect of zonal flow are examined. Good agreement between the two codes is found in the limiting cases and differences in different regimes are discussed.
References
[1] S. Günter et al 2001 Nucl. Fusion 41 1283
[2] A. Di Siena et al 2021 Phys. Rev. Lett. 127 025002
[3] J. Garcia et al 2024 Nat. Commun. 15 7846
[4] W. Deng et al 2022 Phys. Plasmas 29 102106
[5] G. Brochard et al 2024 Phys. Rev. Lett. 132 075101
[6] M. Hoelzl et al 2021 Nucl. Fusion 61 065001
[7] E. Lanti et al 2020 Comput. Phys. Commun. 251 107072
[8] T. J. Bogaarts et al 2022 Phys. Plasmas 29 122501
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