Abstract Details
Abstracts
Author: Chang Liu
Requested Type: Consider for Invited
Submitted: 2024-03-29 15:59:23
Co-authors: Andrey Lvovskiy, Carlos Paz-Soldan, Stephen Jardin, Amitava Bhattacharjee
Contact Info:
Princeton Plasma Physics Laboratory
100 Stellarator Rd
Princeton, New Jersey 08540
USA
Abstract Text:
Alfvénic modes in the current quench (CQ) stage of tokamak disruption have been observed in both DIII-D and ASDEX Upgrade experiments. In DIII-D the excitation of the mode is linked to the presence of high-energy runaway electrons (REs), and a strong mode excitation is often associated with the failure of RE plateau formation. In this work we present results of the first self-consistent kinetic-MHD simulations of RE-driven compressional Alfvén eigenmodes (CAEs) in DIII-D disruption scenarios using the M3D-C1 code [1,2]. It is found that the frequency of the most unstable mode follows a staircase-like function with RE energy, which is consistent with DIII-D experimental observation. Each level of the staircase represents a different mode structure in the poloidal plane. The mode excitation can be explained by considering the resonance between the precession frequency of trapped REs and the CAEs. In the nonlinear simulations with a wide spectrum of RE energies, simultaneous excitation of multiple eigenmodes can be observed which lead to spatial diffusion of REs driven by magnetic perturbations. However, the diffusion effects brought by CAEs are not strong enough to explain fast RE loss observed in experiments.
In summary, the excitation of current quench Alfvénic mode can be explained by considering the resonance between CAEs and the high-energy REs, and can be reproduced using kinetic-MHD simulation. These simulations offer valuable insights into the observed RE loss in experiments and pave the way for the development of innovative RE mitigation strategies.
[1] C. Liu, et al., Phys. Rev. Lett. 131(8), 085102 (2023).
[2] C. Liu, et al., Nucl. Fusion 61, 036011 (2021).
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