Nonlinear control for stabilization of small neoclassical tearing modes in ITER

TitleNonlinear control for stabilization of small neoclassical tearing modes in ITER
Publication TypeJournal Article
Year of Publication2012
AuthorsB.A. Hennen, M. Lauret, G. Hommen, W Heemels, MR de Baar, E. Westerhof
JournalNuclear Fusion
Volume52
Number6
Pagination063007
Date PublishedJun
Type of ArticleArticle
ISBN Number0029-5515
KeywordsCURRENT DRIVE, ELECTRON-CYCLOTRON WAVES, TOKAMAK
Abstract

In this paper, the feasibility of feedback stabilization of neoclassical tearing modes at small island sizes, corresponding to otherwise unstable island sizes in ITER scenario 2, is demonstrated. The islands are stabilized by application of electron cyclotron resonance heating and current drive in a regime where the application of current drive in open loop normally results in a complete suppression of the island. By applying current drive in closed loop with feedback of real-time measurements of the island width, complete suppression is avoided and the island is stabilized at a specific reduced size. In contrast to complete suppression, control of islands at a specific size will allow the manipulation of a plasma's current density profile in hybrid scenarios. Three conceptual (non-)linear feedback controllers with varying complexity, performance, robustness and required model knowledge are introduced. Simulations show the theoretical feasibility of small island stabilization at a specific reduced width. The controllers are applied to the generalized Rutherford equation, which governs the island evolution subject to electron cyclotron current drive. A strategy for the gradual implementation of the controllers is suggested. Stabilization of small islands by feedback control will allow the use of system identification to extend the model knowledge on the evolution of small islands, and in addition will extend the operational regime.

DOI10.1088/0029-5515/52/6/063007
Division

FP

Department

TP

PID

462408b12d9999bed675160bb4c26465

Alternate TitleNucl. Fusion
LabelOA

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