The physics of sawtooth stabilization

被引：56

作者：

Chapman, I. T. ^{[1
]}

Pinches, S. D. ^{[1
]}

Graves, J. P. ^{[2
]}

Akers, R. J. ^{[1
]}

Appel, L. C. ^{[1
]}

Budny, R. V. ^{[3
]}

Coda, S. ^{[2
]}

Conway, N. J. ^{[1
]}

de Bock, M. ^{[4
]}

Eriksson, L-G ^{[5
]}

Hastie, R. J. ^{[1
]}

Hender, T. C. ^{[1
]}

Huysmans, G. T. A. ^{[5
]}

Johnson, T. ^{[6
]}

Koslowski, H. R. ^{[7
]}

Kraemer-Flecken, A. ^{[7
]}

Lennholm, M. ^{[5
]}

Liang, Y. ^{[7
]}

Saarelma, S. ^{[1
]}

Sharapov, S. E. ^{[1
]}

Voitsekhovitch, I. ^{[1
]}

机构：

[1] UKAEA Euratom Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England

[2] Ecole Polytech Fed Lausanne, Assoc Euratom Confederat Suisse, Ctr Rech Phys Plasmas, CH-1007 Lausanne, Switzerland

[3] Princeton Univ, Princeton Plasma Phys Lab, Princeton, NJ 08543 USA

[4] EURATOM, FOM Inst Plasma Phys Rijnhuizen, NL-3430 BE Nieuwegein, Netherlands

[5] CEA Cadarache, Assoc Euratom CEA, F-13108 St Paul Les Durance, France

[6] Assoc EURATOM VR, KTH, SE-10044 Stockholm, Sweden

[7] FZ Julich GmbH, Assoc EURATOM FZ Julich, D-52425 Julich, Germany

来源：

PLASMA PHYSICS AND CONTROLLED FUSION | 2007年 / 49卷 / 12B期

关键词：

D O I：

10.1088/0741-3335/49/12B/S35

中图分类号：

O35 [流体力学]; O53 [等离子体物理学];

学科分类号：

070204 ; 080103 ; 080704 ;

摘要：

Long period sawteeth have been observed to result in low-beta triggering of neo-classical tearing modes, which can significantly degrade plasma confinement. Consequently, a detailed physical understanding of sawtooth behaviour is critical, especially for ITER where fusion-born a particles are likely to lead to very long sawtooth periods. Many techniques have been developed to control, and in particular to destabilize the sawteeth. The application of counter-current neutral beam injection (NBI) in JET has resulted in shorter sawtooth periods than in Ohmic plasmas. This result has been explained because, firstly, the counter-passing fast ions give a destabilizing contribution to the n=1 internal kink mode-which is accepted to be related to sawtooth oscillations-and secondly, the flow shear strongly influences the stabilizing trapped particles. A similar experimental result has been observed in counter-NBI heated plasmas in MAST. However, the strong toroidal flows in spherical tokamaks mean that the sawtooth behaviour is determined by the gyroscopic flow stabilization of the kink mode rather than kinetic effects. In NBI heated plasmas in smaller conventional aspect-ratio tokamaks, such as TEXTOR, the flow and kinetic effects compete to give different sawtooth behaviour. Other techniques applied to destabilize sawteeth are the application of electron cyclotron current drive (ECCD) or ion cyclotron resonance heating (ICRH). In JET, it has been observed that localized ICRH is able to destabilize sawteeth which were otherwise stabilized by a co-existing population of energetic trapped ions in the core. This is explained through the dual role of the ICRH in reducing the critical magnetic shear required to trigger a sawtooth crash, and the increase in the local magnetic shear which results from driving current near the q=1 rational surface. Sawtooth control in ITER could be provided by a combination of ECCD and co-passing off-axis negative-NBI fast ions.

引用

页码：B385 / B394

页数：10

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