A detailed understanding of island seeding is crucial to avoid neoclassical tearing modes and their negative consequences like confinement degradation and disruptions. In the present work, we investigate the growth of 2/1 islands in response to magnetic perturbations. Although we use externally applied perturbations produced by resonant magnetic perturbation (RMP) coils for this study, the results are directly transferable to island seeding by other MHD instabilities creating a resonant magnetic field component at the rational surface. Experimental results for 2/1 island penetration from ASDEX Upgrade are presented extending previous studies. Simulations are based on an ASDEX Upgrade L-mode discharge with low collisionality and active RMP coils. Our numerical studies are performed with the 3D, two-fluid, nonlinear MHD code JOREK. All three phases of mode seeding observed in the experiment are also seen in the simulations: first, a weak response phase characterized by large perpendicular electron flow velocities followed by a fast growth of the magnetic island size accompanied by a reduction of the perpendicular electron velocity and finally the saturation to a fully formed island state with perpendicular electron velocity close to zero. Thresholds for mode penetration are observed in the plasma rotation as well as in the RMP coil current. A hysteresis of the island size and electron perpendicular velocity is observed between the ramping up and down of the RMP amplitude consistent with an analytically predicted bifurcation. The transition from dominant kink/bending to tearing parity during the penetration is investigated.
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April 2019
Research Article|
April 15 2019
Numerical study of tearing mode seeding in tokamak X-point plasma
Dmytro Meshcheriakov;
Dmytro Meshcheriakov
a)
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
2
Max-Planck/Princeton Research Center for Plasma Physics
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Matthias Hoelzl
;
Matthias Hoelzl
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Valentin Igochine
;
Valentin Igochine
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Sina Fietz;
Sina Fietz
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Francois Orain
;
Francois Orain
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
3
CPHT, Ecole Polytechnique
, 91128 Palaiseau Cedex, France
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Guido T. A. Huijsmans
;
Guido T. A. Huijsmans
4
CEA Cadarache, IRFM
, 13108 St. Paul Lez Durance Cedex, France
5
Technische Universiteit Eindhoven
, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Marc Maraschek;
Marc Maraschek
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Mike Dunne;
Mike Dunne
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Rachael McDermott
;
Rachael McDermott
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Hartmut Zohm
;
Hartmut Zohm
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Karl Lackner;
Karl Lackner
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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Sibylle Günter;
Sibylle Günter
1
Max Planck Institute for Plasma Physics
, Boltzmannstr. 2, 85748 Garching b.M., Germany
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b)
See author list of MST1 Team in H. Meyer et al., Nucl. Fusion 57, 102014 (2017).
Physics of Plasmas 26, 042504 (2019)
Article history
Received:
December 20 2018
Accepted:
March 15 2019
Citation
Dmytro Meshcheriakov, Matthias Hoelzl, Valentin Igochine, Sina Fietz, Francois Orain, Guido T. A. Huijsmans, Marc Maraschek, Mike Dunne, Rachael McDermott, Hartmut Zohm, Karl Lackner, Sibylle Günter, ASDEX Upgrade Team, EUROfusion MST1 Team; Numerical study of tearing mode seeding in tokamak X-point plasma. Physics of Plasmas 1 April 2019; 26 (4): 042504. https://doi.org/10.1063/1.5086402
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