Speaker
Description
We present a model of toroidal Alfvén eigenmode (TAE)-driven zonal modes (ZM) producing transport barriers in fusion plasmas. The model is constructed based on the scenarios where a sustained energetic particle source strongly drives toroidal Alfvén eigenmodes (TAE), and phase-space transport is insufficient to saturate TAE. With the sustained EP profile and strongly excited TAE, the interactions between TAEs and directly driven ZM lead to an interesting self-organized state of the system, in which EP energy is deposited into thermals via ZM, along with the formation of a TAE-driven ITB for the thermals.
Zonal modes are directly driven by Reynolds and Maxwell stresses, without the onset of modulational instability, and are damped by collisional and collisionless drag processes. This, in turn, influences the evolution of the TAE via wave-ZM interaction. ZM damping regulates the TAE saturation level and the oscillations of TAE and ZM as they approach saturation. This regulation leads to bursty TAE spectral oscillations, which overshoot approaching saturation. The geodesic acoustic transference (GAT) is a relevant collisionless damping mechanism, which requires sufficient turbulent mixing to be effective. The saturated zonal shears are sufficient to suppress ambient drift-ITG turbulence, leading to a novel enhanced core confinement regime. Heating by both collisional and collisionless ZM damping ultimately deposits alpha particle energy into the thermal plasma, achieving effective alpha channeling. As a result, EP transport is connected to thermal turbulence by cross-scale interactions.
| Presentation type | Oral |
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