Nonlinear dynamics of Shear Alfvén fluctuations in Divertor Tokamak Test facility plasmas

Abstract

Following the analysis on linear spectra of shear Alfvén fluctuations excited by energetic particles (EPs) in the Divertor Tokamak Test (DTT) facility plasmas [T. Wang et al., Phys. Plasmas 25, 062509 (2018)], in this work, nonlinear dynamics of the corresponding mode saturation and the fluctuation induced EP transport is studied by hybrid magnetohydrodynamic-gyrokinetic simulations. For the reversed shear Alfvén eigenmode driven by magnetically trapped EP precession resonance in the central core region of DTT plasmas, the saturation is mainly due to radial decoupling of resonant trapped EPs. Consistent with the wave-EP resonance structure, EP transport occurs in a similar scale to the mode width. On the other hand, passing EP transport is analyzed in detail for toroidal Alfvén eigenmode in the outer core region, with mode drive from both passing and trapped EPs. It is shown that passing EPs experience only weak redistributions in the weakly unstable case; and the transport extends to meso-scale diffusion in the strongly unstable case, due to orbit stochasticity induced by resonance overlap. Here, weakly/strongly unstable regime is determined by Chirikov condition for resonance overlap. This work then further illuminates rich and diverse nonlinear EP dynamics related to burning plasma studies, and the capability of DTT to address these key physics.

arXiv comment32 pages, 20 figures

References in corpus (4)

• Nonlinear dynamics of phase space zonal structures and energetic particle physics in fusion plasmas
• Energetic particle instabilities in fusion plasmas
• An extended hybrid magnetohydrodynamics gyrokinetic model for numerical simulation of shear Alfvén waves in burning plasmas
• Nonlinear dynamics of beta induced Alfvén eigenmode driven by energetic particles

Cited by in corpus (5)

• Shear Alfvén and acoustic continuum in general axisymmetric toroidal geometry
• Nonlinear excitation of geodesic acoustic mode by toroidal Alfvén eigenmodes and impact on plasma performance
• Nonlinear reversed shear Alfven eigenmode saturation due to spontaneous zonal current generation
• Dynamics of reversed shear Alfvén eigenmode and energetic particles during current ramp-up
• Zero frequency zonal flow excitation by energetic electron driven beta-induced Alfven eigenmode