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Author: Don A. Spong
Requested Type: Poster
Submitted: 2018-03-01 15:21:46

Co-authors: J. Varela, L. Garcia

Contact Info:
Oak Ridge National Laboratory
One Bethel Valley Road
Oak Ridge, TN   37831-6

Abstract Text:
The aim of this study is to analyze the destabilization of Alfven Eigenmodes (AE) by energetic particles (EP) in ITER steady state discharges using a global model. We use the reduced MHD equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moments of two energetic particle sources: neutral beam injectors (NBI) and alpha particles, including acoustic modes and two fluid effects. We add the Landau damping and resonant destabilization effects using a closure relation. The results show that the AEs are mainly destabilized by alpha particle drive. In addition, modifying the NBI injection intensity, beam energy or energetic particle density profile only slightly changes the AE growth rate and frequency, although the combined effect of alpha and NBI energetic particles leads to AEs with lower growth rates compared with AEs destabilized by NBI or alpha energetic particles individually, pointing out a stabilizing effect of the NBI energetic particles over alpha particles driven AE. The AEs destabilized are n > 11 toroidal AE (TAE) localized in the reverse shear region ('n' is the toroidal number) showing a larger toroidal coupling compared to low n TAE (n < 11), that are stable. If the NBI energetic particle β > 0.001, n < 16, beta induced AEs (BAE) are destabilized near the magnetic axis, showing a growth rates 2 times larger than TAEs growth rate with frequencies around 15 kHz. On the other hand, if alpha particle β > 0.01, n < 14 elliptical or non circular AE (EAE / NAE) are destabilized in the reverse shear region with growth rates 2 times larger than the TAEs with frequencies around 175 kHz.