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Radiative and continuum dampings of reversed shear Alfvén eigenmodes and perturbative analysis limitations for tokamaks

Published online by Cambridge University Press:  29 November 2024

N. N. Gorelenkov Open the ORCID record for N. N. Gorelenkov [Opens in a new window] ,
L. Yu ,
Y. Wang  and
G.-Y. Fu Open the ORCID record for G.-Y. Fu [Opens in a new window]
N. N. Gorelenkov*
Affiliation:
Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08543-0451, USA
L. Yu
Affiliation:
School of Physics, East China University of Science and Technology, Shanghai 200237, PR China
Y. Wang
Affiliation:
Institute for Fusion Theory and Simulation and School of Physics, Zhejiang University, Hangzhou 310027, PR China
G.-Y. Fu
Affiliation:
Institute for Fusion Theory and Simulation and School of Physics, Zhejiang University, Hangzhou 310027, PR China
*
†Email address for correspondence: [email protected]
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Abstract

A careful theoretical analysis of the excitation of Alfvén eigenmodes (AEs), such as TAE (toroidicity-induced AE) and RSAE (reversed shear AE), by superalfvenic energetic particles is required for reliable predictions of energetic ion relaxation in present day fusion experiments. This includes the evaluation of different AE damping mechanisms including radiative and continuum dampings which are the focus of this study. A recent comprehensive benchmark of different eigenmode solvers including gyrokinetic, gyrofluid and hybrid magenetohydrodynamics (MHD) has shown that employed models may have deficiencies when addressing some of them (Taimourzadeh et al., Nucl. Fusion, vol. 59, 2019, 066006). In this paper, we are studying the radiative and continuum dampings of RSAEs in details which were missing in hybrid NOVA/NOVA-C calculations to prepare a NOVA-C package with a substantial upgrade. Both dampings require the finite Larmor radius (FLR) corrections to AE mode structures to be accounted for. Accurately calculating different damping rates and understanding their parametric dependencies, we resolve the limitation coming out of the perturbative approach. In particular, here, the radiative damping is included perturbatively, whereas the continuum damping is computed non-perturbatively. Our comparison leads to the conclusion that the non-perturbative treatment of the unstable RSAE modes is needed to find the agreement with the gyrokinetic calculations. We expect that the RSAE mode structure modification plays a dominant role in determining the RSAE stability.

Keywords

fusion plasmaplasma wavesplasma instabilities
Type
Research Article
Information
Journal of Plasma Physics , Volume 90 , Issue 6 , December 2024 , 905900607
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Copyright
Copyright © The Author(s), 2024. Published by Cambridge University Press

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