Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus

H.J.C. Oliver; S.E. Sharapov; B.N. Breizman; L.J. Zheng; Leena Aho-Mantila; Markus Airila; Antti Hakola; Seppo Koivuranta; Jari Likonen; Antti Salmi; Paula Sirén; Tuomas Tala; JET Contributors

doi:10.1063/1.5005939

Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus

H.J.C. Oliver^*
, S.E. Sharapov
, B.N. Breizman
, L.J. Zheng
, Leena Aho-Mantila
, Markus Airila
, Antti Hakola
, Seppo Koivuranta
, Jari Likonen
, Antti Salmi
, Paula Sirén
, Tuomas Tala
, JET Contributors

^*Corresponding author for this work

The University of Texas at Dallas
Culham Science Centre
Forschungszentrum Jülich GmbH (FZJ)
Institute for Plasma Research
Universidade de Lisboa
Queen's University Belfast
University of Helsinki
Commissariat a l'Energie Atomique et aux Energies Alternatives (CEA)
National Institutes for Quantum Science and Technology (QST)
University of Naples Federico II
National University of Distance Education
National Research Council (CNR)
ITER Organization
Petersburg Nuclear Physics Institute
Parthenope University of Naples
National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA)
Troitsk Institute for Innovation and Fusion Research
Uppsala University
National Institute for Cryogenics and Isotopic Technology
Max-Planck-Institut für Plasmaphysik (IPP)
Aalto University
Seoul National University
Institute of Plasma Physics (ASIPP CAS)
Chalmers University of Technology

Research output: Contribution to journal › Article › Scientific › peer-review

28 Citations (Scopus)

Abstract

Alfvén eigenmodes (AEs) with toroidal mode number n = 0 (i.e., axisymmetric) have been observed in the ellipticity-induced frequency range in the Joint European Torus. The axisymmetric modes are of interest because they can be used to diagnose fast particle energy distributions at the mode location. The modes were identified as global Alfvén eigenmodes (GAEs), with the ellipticity of the plasma cross-section preventing strong continuum damping of the modes. The MHD codes CSCAS, MISHKA, and AEGIS were used to compute the n = 0 Alfvén continuum, eigenmode structure, and continuum damping. For zero ellipticity, a single mode exists at a frequency below the Alfvén continuum branch. This mode has two dominant poloidal harmonics with poloidal mode numbers m = ±1 that have the same polarity; therefore, it is an even mode. For finite ellipticity, the continuum branch splits into two branches and the single GAE splits into two modes. An even mode exists below the minimum of the top continuum branch, and the frequency of this mode coincides with the experimentally observed AE frequency. The other mode is found below the lower continuum branch with opposite signs between the two poloidal harmonics (an odd mode structure). This mode was not excited in our experiment. Analytical theory for the n = 0 GAE in an elliptical cylinder shows the n = 0 Alfvén continuum agrees with the numerical modelling.

Original language	English
Article number	122505
Journal	Physics of Plasmas
Volume	24
Issue number	12
DOIs	https://doi.org/10.1063/1.5005939
Publication status	Published - 1 Dec 2017
MoE publication type	A1 Journal article-refereed

Funding

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under Grant Agreement No. 633053 and from the RCUK Energy Programme [Grant No. EP/P012450/1]. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This research was supported by the Office of Fusion Energy Science of the U.S. Department of Energy under Grant No. DE-FG02-04ER54742. AEGIS calculations used resources of the National Energy Research Scientific Computing Center, a Department of Energy Office of Science User Facility supported under Contract No. DE-AC02-05CH11231.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 7 Affordable and Clean Energy

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10.1063/1.5005939

Cite this

Oliver, H. J. C., Sharapov, S. E., Breizman, B. N., Zheng, L. J., Aho-Mantila, L., Airila, M., Hakola, A., Koivuranta, S., Likonen, J., Salmi, A., Sirén, P., Tala, T., & JET Contributors (2017). Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus. Physics of Plasmas, 24(12), Article 122505. https://doi.org/10.1063/1.5005939

@article{e4e04c0385ee42d7ac1216a45b18b0bf,

title = "Axisymmetric global Alfv{\'e}n eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus",

abstract = "Alfv{\'e}n eigenmodes (AEs) with toroidal mode number n = 0 (i.e., axisymmetric) have been observed in the ellipticity-induced frequency range in the Joint European Torus. The axisymmetric modes are of interest because they can be used to diagnose fast particle energy distributions at the mode location. The modes were identified as global Alfv{\'e}n eigenmodes (GAEs), with the ellipticity of the plasma cross-section preventing strong continuum damping of the modes. The MHD codes CSCAS, MISHKA, and AEGIS were used to compute the n = 0 Alfv{\'e}n continuum, eigenmode structure, and continuum damping. For zero ellipticity, a single mode exists at a frequency below the Alfv{\'e}n continuum branch. This mode has two dominant poloidal harmonics with poloidal mode numbers m = ±1 that have the same polarity; therefore, it is an even mode. For finite ellipticity, the continuum branch splits into two branches and the single GAE splits into two modes. An even mode exists below the minimum of the top continuum branch, and the frequency of this mode coincides with the experimentally observed AE frequency. The other mode is found below the lower continuum branch with opposite signs between the two poloidal harmonics (an odd mode structure). This mode was not excited in our experiment. Analytical theory for the n = 0 GAE in an elliptical cylinder shows the n = 0 Alfv{\'e}n continuum agrees with the numerical modelling.",

author = "H.J.C. Oliver and S.E. Sharapov and B.N. Breizman and L.J. Zheng and X. Litaudon and S. Abduallev and M. Abhangi and P. Abreu and M. Afzal and K.M. Aggarwal and T. Ahlgren and Ahn, \{J. H.\} and Leena Aho-Mantila and N. Aiba and Markus Airila and R. Albanese and V. Aldred and D. Alegre and E. Alessi and P. Aleynikov and A. Alfier and A. Alkseev and M. Allinson and B. Alper and E. Alves and G. Ambrosino and R. Ambrosino and L. Amicucci and V. Amosov and Sund{\'e}n, \{E. Andersson\} and M. Angelone and M. Anghel and C. Angioni and L. Appel and C. Appelbee and Antti Hakola and Anssi J{\"a}rvinen and J. Karhunen and H.T. Kim and H.S. Kim and Seppo Koivuranta and A. Lahtinen and Jari Likonen and Y. Liu and T. Makkonen and H. Nordman and Antti Salmi and M.I.K. Santala and Paula Sir{\'e}n and Tuomas Tala and \{JET Contributors\}",

note = "Publisher Copyright: {\textcopyright} 2017 EURATOM.",

year = "2017",

month = dec,

day = "1",

doi = "10.1063/1.5005939",

language = "English",

volume = "24",

journal = "Physics of Plasmas",

issn = "1070-664X",

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TY - JOUR

T1 - Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus

AU - Oliver, H.J.C.

AU - Sharapov, S.E.

AU - Breizman, B.N.

AU - Zheng, L.J.

AU - Litaudon, X.

AU - Abduallev, S.

AU - Abhangi, M.

AU - Abreu, P.

AU - Afzal, M.

AU - Aggarwal, K.M.

AU - Ahlgren, T.

AU - Ahn, J. H.

AU - Aho-Mantila, Leena

AU - Aiba, N.

AU - Airila, Markus

AU - Albanese, R.

AU - Aldred, V.

AU - Alegre, D.

AU - Alessi, E.

AU - Aleynikov, P.

AU - Alfier, A.

AU - Alkseev, A.

AU - Allinson, M.

AU - Alper, B.

AU - Alves, E.

AU - Ambrosino, G.

AU - Ambrosino, R.

AU - Amicucci, L.

AU - Amosov, V.

AU - Sundén, E. Andersson

AU - Angelone, M.

AU - Anghel, M.

AU - Angioni, C.

AU - Appel, L.

AU - Appelbee, C.

AU - Hakola, Antti

AU - Järvinen, Anssi

AU - Karhunen, J.

AU - Kim, H.T.

AU - Kim, H.S.

AU - Koivuranta, Seppo

AU - Lahtinen, A.

AU - Likonen, Jari

AU - Liu, Y.

AU - Makkonen, T.

AU - Nordman, H.

AU - Salmi, Antti

AU - Santala, M.I.K.

AU - Sirén, Paula

AU - Tala, Tuomas

AU - JET Contributors

PY - 2017/12/1

Y1 - 2017/12/1

N2 - Alfvén eigenmodes (AEs) with toroidal mode number n = 0 (i.e., axisymmetric) have been observed in the ellipticity-induced frequency range in the Joint European Torus. The axisymmetric modes are of interest because they can be used to diagnose fast particle energy distributions at the mode location. The modes were identified as global Alfvén eigenmodes (GAEs), with the ellipticity of the plasma cross-section preventing strong continuum damping of the modes. The MHD codes CSCAS, MISHKA, and AEGIS were used to compute the n = 0 Alfvén continuum, eigenmode structure, and continuum damping. For zero ellipticity, a single mode exists at a frequency below the Alfvén continuum branch. This mode has two dominant poloidal harmonics with poloidal mode numbers m = ±1 that have the same polarity; therefore, it is an even mode. For finite ellipticity, the continuum branch splits into two branches and the single GAE splits into two modes. An even mode exists below the minimum of the top continuum branch, and the frequency of this mode coincides with the experimentally observed AE frequency. The other mode is found below the lower continuum branch with opposite signs between the two poloidal harmonics (an odd mode structure). This mode was not excited in our experiment. Analytical theory for the n = 0 GAE in an elliptical cylinder shows the n = 0 Alfvén continuum agrees with the numerical modelling.

AB - Alfvén eigenmodes (AEs) with toroidal mode number n = 0 (i.e., axisymmetric) have been observed in the ellipticity-induced frequency range in the Joint European Torus. The axisymmetric modes are of interest because they can be used to diagnose fast particle energy distributions at the mode location. The modes were identified as global Alfvén eigenmodes (GAEs), with the ellipticity of the plasma cross-section preventing strong continuum damping of the modes. The MHD codes CSCAS, MISHKA, and AEGIS were used to compute the n = 0 Alfvén continuum, eigenmode structure, and continuum damping. For zero ellipticity, a single mode exists at a frequency below the Alfvén continuum branch. This mode has two dominant poloidal harmonics with poloidal mode numbers m = ±1 that have the same polarity; therefore, it is an even mode. For finite ellipticity, the continuum branch splits into two branches and the single GAE splits into two modes. An even mode exists below the minimum of the top continuum branch, and the frequency of this mode coincides with the experimentally observed AE frequency. The other mode is found below the lower continuum branch with opposite signs between the two poloidal harmonics (an odd mode structure). This mode was not excited in our experiment. Analytical theory for the n = 0 GAE in an elliptical cylinder shows the n = 0 Alfvén continuum agrees with the numerical modelling.

UR - https://www.scopus.com/pages/publications/85038566645

U2 - 10.1063/1.5005939

DO - 10.1063/1.5005939

M3 - Article

AN - SCOPUS:85038566645

SN - 1070-664X

VL - 24

JO - Physics of Plasmas

JF - Physics of Plasmas

IS - 12

M1 - 122505

ER -

Axisymmetric global Alfvén eigenmodes within the ellipticity-induced frequency gap in the Joint European Torus

Abstract

Funding

UN SDGs

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