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Title: Experiment-theory comparison for low frequency BAE modes in the strongly shaped H-1NF stellarator

Here, recent advances in the modeling, analysis, and measurement of fluctuations have significantly improved the diagnosis and understanding of Alfvén eigenmodes in the strongly shaped H-1NF helical axis stellarator. Experimental measurements, including 3D tomographic inversions of high resolution visible light images, are in close agreement with beta-induced Alfvén eigenmodes (BAEs) calculated using the compressible ideal MHD code, CAS3D. This is despite the low β in H-1NF, providing experimental evidence that these modes can exist due to compression that is induced by the strong shaping in stellarators, in addition to high β, as is the case in tokamaks. This is confirmed using the CONTI and CAS3D codes, which show significant gap structures at lower frequencies which contain BAE and beta-acoustic Alfvén eigenmodes (BAAEs). The BAEs are excited in the absence of a well confined energetic particle source, further confirming previous studies that thermal particles, electrons, or even radiation fluctuations can drive these modes. Datamining of magnetic probe data shows the experimentally measured frequency of these modes has a clear dependence on the rotational transform profile, which is consistent with a frequency dependency due to postulated confinement related temperature variations.
ORCiD logo [1] ;  [1] ;  [2] ;  [2] ;  [3] ; ORCiD logo [3] ;  [3] ;  [3]
  1. The Australian National Univ., Canberra, ACT (Australia); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Max-Planck-Institut fur Plasmaphysik, Greifswald (Germany)
  3. The Australian National Univ., Canberra, ACT (Australia)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 9; Journal ID: ISSN 0741-3335
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
Country of Publication:
United States
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Alfven waves; beta induced alfven eigenmodes; global alfven eigenmodes; MHD instabilities; BAE
OSTI Identifier: