TY - JOUR
T1 - Experiment-theory comparison for low frequency BAE modes in the strongly shaped H-1NF stellarator
AU - Haskey, S. R.
AU - Blackwell, B. D.
AU - Nührenberg, C.
AU - Könies, A.
AU - Bertram, J.
AU - Michael, C.
AU - Hole, M. J.
AU - Howard, J.
N1 - Publisher Copyright:
© 2015 IOP Publishing Ltd.
PY - 2015/8/12
Y1 - 2015/8/12
N2 - 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.
AB - 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.
KW - Alfven waves
KW - BAE
KW - beta induced alfven eigenmodes
KW - global alfven eigenmodes
KW - MHD instabilities
UR - https://www.scopus.com/pages/publications/84942936047
UR - https://www.scopus.com/pages/publications/84942936047#tab=citedBy
U2 - 10.1088/0741-3335/57/9/095011
DO - 10.1088/0741-3335/57/9/095011
M3 - Article
AN - SCOPUS:84942936047
SN - 0741-3335
VL - 57
JO - Plasma Physics and Controlled Fusion
JF - Plasma Physics and Controlled Fusion
IS - 9
M1 - 095011
ER -