Integrated modelling of island growth, stabilization and mode locking: consequences for NTM control on ITER

TitleIntegrated modelling of island growth, stabilization and mode locking: consequences for NTM control on ITER
Publication TypeJournal Article
Year of Publication2012
AuthorsH. van den Brand, MR de Baar, N.JL Cardozo, E. Westerhof
JournalPlasma Physics and Controlled Fusion
Volume54
Number9
Pagination094003
Date PublishedSep
Type of ArticleArticle; Proceedings Paper
ISBN Number0741-3335
KeywordsBEAM, CURRENT DRIVE, ELECTRON-CYCLOTRON WAVES, INSTABILITIES, NEOCLASSICAL TEARING MODES, PERTURBATIONS, TOKAMAK PLASMAS
Abstract

Full suppression of neoclassical tearing modes (NTMs) using electron cyclotron current drive (ECCD) should be reached before mode locking (stop of rotation) makes suppression impossible. For an ITER scenario 2 plasma, the similar time scales for locking and island growth necessitate the combined modelling of the growth of the mode and its slow down due to wall induced drag. Using such a model, the maximum allowed latency between the seeding of the mode and the start of ECCD deposition and maximum deviation in the radial position are determined. The maximum allowed latency is determined for two limiting models for island growth; the polarization model with W-marg = 2 cm, representing the worst case, and the transport model with W-marg = 6 cm, representing the best case. NTMs with seed island widths up to 9.5 cm and 12 cm for the 2/1 and the 3/2 NTM, respectively, are suppressible. The maximum allowed latency is 1.05 s and 2.95 s for the 2/1 and 3/2 NTM, respectively, for the worst case model. Radial misalignment should not exceed 7-10 mm for the 2/1 NTM and 5-16 mm for the 3/2 NTM depending on the model for island growth. As long as the alignment suffices, it does not reduce the maximum allowed latency. Mode locking has serious implications for any real-time NTM control system on ITER that aims to suppress NTMs by ECCD.

DOI10.1088/0741-3335/54/9/094003
Division

FP

Department

TP

PID

86f34d6ccc8a87260703d4d3b75599e7

Alternate TitlePlasma Phys. Control. Fusion
LabelOA

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