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#88
Kinetic-MHD simulation of compressional Alfvén eigenmodes excited by runaway electrons Oral Remote
Chang Liu (Princeton Plasma Physics Laboratory)
Andrey Lvovskiy, Carlos Paz-Soldan, Stephen Jardin, Amitava Bhattacharjee
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PDF, 2023-06-20 11:44:17
SCHEDULED This contribution is scheduled to be presented on Tuesday 20th 16:30-17:00
Abstract
The avalanche of runaway electrons in tokamak disruption poses a significant challenge to the success of ITER, SPARC and future fusion devices based on tokamaks. The interaction between runaway electrons and plasma waves have been proposed as a mechanism to mitigate runaway electron beams. DIII-D and ASDEX disruption experiments have illustrated that high energy runaway electrons can lead to excitation of plasma waves in the 0.3-3 MHz frequency range, which is often associated with fast diffusion of runaway electrons and failure of a runaway electron current plateau formation. In this work we did a self-consistent simulation of excitation of compressional Alfvén eigenmodes (CAEs) driven by runaway electrons in DIII-D disruption scenarios, and studied the impact on the confinement of runaway electrons. We utilized the kinetic-MHD code M3D-C1-K, in which the runaway electron beam is simulated using PIC method, and the plasma wave fluctuation is simulated using M3D-C1. In our simulation we found the high energy trapped runaway electrons can have resonance with the Alfvén mode through their precession motion, and the resonance frequency is proportional to the energy of relativistic electrons. For a runaway electron tail with a wide energy spectrum (4MeV-20MeV), several discrete modes can be excited simultaneously, which is consistent with experimental observation. It is also found that the overlapping of multiple modes can lead to fast diffusion of runaway electrons, if the perturbed magnetic fields from the mode exceeds a certain threshold. This work shows that Alfvén mode is an alternative approach to mitigate runaway electrons. The efficiency of beam dissipation depends on the mode amplitude, which can be studied using kinetic simulation models targeting different devices. This work was supported by the Simulation Center of electrons (SCREAM) SciDAC center by Office of Fusion Energy Science and Office of Advanced Scientific Computing of U. S. Department of Energy, under contract No. DE-SC0016268 and DE-AC02-09CH11466.
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