Speaker
Description
Negative triangularity (NT) shaped plasmas emerge as an attractive scenario with high fusion performance and power handling capabilities. Recent experiments at the TCV and DIII-D tokamaks have demonstrated fusion-relevant ELM-free H-mode like confinement levels. While NT shaped plasmas have shown little to no effect on fast-ions in DIII-D [1], a mitigation of fast-ion driven Toroidally induced Alfvén Eigenmodes (TAEs) have been observed at TCV [2]. Consistently with TCV observations, non-linear hybrid-kinetic MHD simulations reveal a lower wave-particle energy exchange between the energetic particles and the experimentally observed TAEs in NT when compared with its counterpart in Positive Triangularity (PT). Changes in the magnetic topology are found to modify the fast-ion orbits and, thus, the underlying wave-particle resonances.
Strongly anisotropic fast-ion distribution functions tend to drive Geodesic Acoustic Modes (EGAMs) unstable in current tokamaks as observed for instance in DIII-D [3], AUG [4] and TCV [5]. In this work, MEGA simulations are carried out to study the role that unstable EGAMs may play in the TAE stability / mitigation observed at the TCV tokamak in NT shaped plasmas. A preliminary study for spherical tokamaks with SMART plasmas as reference scenarios will be presented.
[1] M. A. Van Zeeland et al., Nucl. Fusion 59, 086028 (2019)
[2] P. Oyola et al., in preparation
[3] R. Nazikian et al., Phys. Rev. Lett. 101, 185001 (2008)
[4] B. Rettino et al., Nucl. Fusion 62, 076027 (2022)
[5] A. J. Van Vuuren et al., 66th APS Division of Plasma Physics Meeting, Atlanta (2024)
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