Probing non-linear MHD stability of the EDA H-mode in ASDEX Upgrade

Nuclear Fushion

article

A. Cathey¹  M. Hoelzl¹  L. Gil²  M.G. Dunne¹  G.F. Harrer³  G.T.A. Huijsmans⁴  J. Kalis¹  K. Lackner¹  S.J.P. Pamela⁷  E. Wolfrum¹  S. Günter¹ 

[1] Max Planck Institute for Plasma Physics;Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa;Institute of Applied Physics;CEA;Eindhoven University of Technology;Physik Department E28, Technische Universität München;CCFE, Culham Science Centre

关键词: plasma physics;    magnetic confinement;    non-linear simulations;    magnetohydrodynamics;    edge localised modes;   

DOI  :  10.1088/1741-4326/acc818

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Regimes of operation in tokamaks that are devoid of large edge localised modes have to be better understood to extrapolate their applicability to reactor-relevant devices. This paper describes non-linear extended magnetohydrodynamic (MHD) simulations that use an experimental equilibrium from an enhanced D-alpha (EDA) H-mode in ASDEX Upgrade. Linear ideal MHD analysis indicates that the operational point lies slightly inside of the stable region. The non-linear simulations with the visco-resistive extended MHD code, JOREK, sustain non-axisymmetric perturbations that are linearly most unstable with toroidal mode numbers of {n = {6ldots9}} , but non-linearly higher and lowernbecome driven and the low- nbecome dominant. The poloidal mode velocity during the linear phase is found to correspond to the expected velocity for resistive ballooning modes. The perturbations that exist in the simulations have somewhat smaller poloidal wavenumbers (k_hetasim0.1 –0.5~mathrm{cm^{-1}} ) than the experimental expectations for the quasi-coherent mode in EDA, and cause non-negligible transport in both the heat and particle channels. In the transition from linear to non-linear phase, the mode frequency chirps down from approximately 35 kHz to 13 kHz, which corresponds approximately to the lower end of frequencies that are typically observed in EDA H-modes in ASDEX Upgrade.

【 授权许可】

Unknown