Abstract Details
Abstracts
Author: David Zarzoso
Requested Type: Pre-Selected Invited
Submitted: 2019-02-22 16:10:48
Co-authors: D. del Castillo Negrete
Contact Info:
CNRS
Avenue Escadrille Normandie Ni
Marseille, 13397
France
Abstract Text:
Energetic particles are ubiquitous in fusion plasmas and need to be well-confined in order to transfer their energy to thermal particles and thus achieve self-sustained fusion reactions. However, energetic particles excite modes that tend to de-confine the particles themselves. This is the reason why understanding and controlling energetic particle modes is of prime importance. In this presentation we focus on a special class of modes, called energetic geodesic acoustic modes (EGAMs) [1, 2]. Because these modes are axisymmetric, they have been assumed to play little role on transport. However, experiments in DIII-D provided puzzling and, so far, unexplained evidence that particles can be de-confined in the presence of EGAMs [1]. In this presentation we elucidate the underlying transport mechanism and show that even if the EGAM potential is axisymmetric and not turbulent, a chaotic channel from the inner region to the edge of the tokamak is created [3]. To support this idea, we present full-f gyro-kinetic simulations with the state-of-the-art multi-species GYSELA code where EGAMs are excited [4, 5] and show that transport results from a complex 3D interaction of resonances that make the particle trajectories chaotic. Our gyro-kinetic results are complemented by a reduced model that exhibits novel aspects of particle transport in the presence of EGAMs including fractal behavior and trapping-induced anomalous diffusion.
[1] R. Nazikian et al, Phys. Rev. Lett. 101,185001 (2008)
[2] G. Fu, Phys. Rev. Lett. 101, 185002 (2008)
[3] D. Zarzoso et al., Nucl. Fusion 58 106030 (2018)
[4] D. Zarzoso et al, Phys Rev Lett 110, 125002 (2013)
[5] D. Zarzoso et al., Phys. Plasmas 19, 022102 (2012)
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