Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

TitlePlasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium
Publication TypeJournal Article
Year of Publication2016
AuthorsM. Willensdorfer, S.S Denk, E. Strumberger, W. Suttrop, B. Vanovac, D. Brida, M. Cavedon, I. Classen, M. Dunne, S. Fietz, R. Fischer, A. Kirk, F.M Laggner, Y.Q Liu, T. Odstrcil, D.A Ryan, E. Viezzer, H. Zohm, I.C Luhmann, ASDEX-Upgrade Team, EUROfusion MST1 Team
JournalPlasma Physics and Controlled Fusion
Volume58
Issue11
Number11
Pagination114004
Date PublishedNov
ISBN Number0741-3335
Abstract

The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement around the outboard midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the predictions from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components vertical bar m vertical bar > vertical bar nq vertical bar, whereas the poloidal mode structure of its displacement is almost resonant vertical bar m vertical bar approximate to vertical bar nq vertical bar. This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.

URLhttps://arxiv.org/abs/1603.09150
DOI10.1088/0741-3335/58/11/114004
Division

FP

Department

PEPD

PID

a1e652bc93cbf7fd81c614e73a717c8b

Alternate TitlePlasma Phys. Control. Fusion

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