Edge localized modes (ELMs) are magnetohydrodynamic (MHD) instabilities that cause fast periodic relaxations of the strong edge pressure gradient in tokamak fusion plasmas. Magnetic pick-up coils allow the extraction of toroidal mode numbers n during the ELM cycle including the nonlinear crash on ASDEX Upgrade, providing a good comparability to nonlinear 3D MHD codes. This paper investigates how the mode numbers before and during the ELM crash change with a variation of plasma parameters. It is found that the toroidal structure size during the crash is similar to the one existing slightly before and always has a low n = 1-7 range. Furthermore, in the nonlinear phase of the ELM n does not show a clear trend with most peeling-ballooning relevant parameters such as normalized pressure gradient, bootstrap current density or triangularity, whereas a strong decrease of n with edge safety factor q 95 is observed in agreement with nonlinear modeling in the here investigated high collisionality region. A simple geometric model is presented, which is capable of explaining the q scaling by existence of ballooned structures that minimize n.

Asdex Upgrade Team, T., Mink, A., Wolfrum, E., Dunne, M., Hoelzl, M., Maraschek, M., et al. (2018). Scaling of the toroidal structure and nonlinear dynamics of ELMs on ASDEX Upgrade. PLASMA PHYSICS AND CONTROLLED FUSION, 60(12) [10.1088/1361-6587/aae33a].

Scaling of the toroidal structure and nonlinear dynamics of ELMs on ASDEX Upgrade

Cavedon M.;
2018

Abstract

Edge localized modes (ELMs) are magnetohydrodynamic (MHD) instabilities that cause fast periodic relaxations of the strong edge pressure gradient in tokamak fusion plasmas. Magnetic pick-up coils allow the extraction of toroidal mode numbers n during the ELM cycle including the nonlinear crash on ASDEX Upgrade, providing a good comparability to nonlinear 3D MHD codes. This paper investigates how the mode numbers before and during the ELM crash change with a variation of plasma parameters. It is found that the toroidal structure size during the crash is similar to the one existing slightly before and always has a low n = 1-7 range. Furthermore, in the nonlinear phase of the ELM n does not show a clear trend with most peeling-ballooning relevant parameters such as normalized pressure gradient, bootstrap current density or triangularity, whereas a strong decrease of n with edge safety factor q 95 is observed in agreement with nonlinear modeling in the here investigated high collisionality region. A simple geometric model is presented, which is capable of explaining the q scaling by existence of ballooned structures that minimize n.
Articolo in rivista - Articolo scientifico
edge localized mode; mode number; nonlinear; plasma;
English
Asdex Upgrade Team, T., Mink, A., Wolfrum, E., Dunne, M., Hoelzl, M., Maraschek, M., et al. (2018). Scaling of the toroidal structure and nonlinear dynamics of ELMs on ASDEX Upgrade. PLASMA PHYSICS AND CONTROLLED FUSION, 60(12) [10.1088/1361-6587/aae33a].
Asdex Upgrade Team, T; Mink, A; Wolfrum, E; Dunne, M; Hoelzl, M; Maraschek, M; Fischer, R; Cavedon, M; Harrer, G; Stroth, U
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/354848
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