Stabilization of neoclassical tearing modes using a continuous localized current drive

Pletzer, A.; Perkins, F. W.

doi:10.1063/1.873412

Cited by 73 publications

(92 citation statements)

References 32 publications

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“…Here, I cd /∆ρ 2 is the figure of merit for both the NTM stabilization [23] and the sawtooth period control [24]. Comparison of the results shown in Fig.…”

Section: Angle Scanning For the Equatorial Launchermentioning

confidence: 99%

Electron cyclotron current drive calculated for ITER conditions using different models

2008

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Abstract. The current drive efficiency for the ITER reference Scenario-2 has been calculated by the newly developed ray-tracing code TRAVIS for both the upper and equatorial launcher. For comparison, two adjoint approach models are applied, the high-speed-limit model and a model with the parallel momentum conservation taken into account. It is shown, that in the angle range expected as optimal launch angles the momentum conservation correction produces a non-negligible contribution in ECCD, leading to the necessity to revise the previous predictions carefully. Additionally, the scenario with reduced magnetic field is checked. It is shown, that the ECCD efficiency (as well as the deposition profile) for the equatorial launcher may significantly be changed due to unwanted absorption at the higher (parasitic) harmonics.

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“…Here, I cd /∆ρ 2 is the figure of merit for both the NTM stabilization [23] and the sawtooth period control [24]. Comparison of the results shown in Fig.…”

Section: Angle Scanning For the Equatorial Launchermentioning

confidence: 99%

Electron cyclotron current drive calculated for ITER conditions using different models

2008

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“…full island width normalized to the full 1/e width, for the modulated (50% duty cycle, 100 % modulation depth, O-point and X-point modulation) and the unmodulated case using the literature values a mn =32 [5] and a 00 = 2 [6]. Due to the assumption that the (0,0) term is independent of W, it dominates for large W and actually makes the unmodulated case exceed the modulated case, whereas for small W/(2d), the (m,n) component dominates and consequently the benefits of modulation become evident.…”

Section: The Function ∆' CD = I Eccd (A Mn η Mn (D/w)mentioning

confidence: 99%

Control of MHD instabilities by ECCD: ASDEX Upgrade results and implications for ITER

et al. 2007

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_______________________________________________________________This is a preprint of a paper intended for presentation at a scientific meeting. Because of the provisional nature of its content and since changes of substance or detail may have to be made before publication, the preprint is made available on the understanding that it will not be cited in the literature or in any way be reproduced in its present form. The views expressed and the statements made remain the responsibility of the named author(s); the views do not necessarily reflect those of the government of the designating Member State(s) or of the designating organization(s). In particular, neither the IAEA nor any other organization or body sponsoring this meeting can be held responsible for any material reproduced in this preprint. Abstract. The requirements for control of MHD instabilities by ECCD are reviewed. It is shown that localised current drive is needed for control of both sawteeth and Neoclassical Tearing Modes (NTMs). In the case of NTMs, the deposition width should be smaller than the island width for efficient control. At island widths smaller than the deposition width, as is predicted to occur in ITER, theory suggests that efficient control is possible only by modulating the ECCD power in phase with the island. These predictions are experimentally confirmed in ASDEX Upgrade for NTM control. Narrow deposition has also been used to extend the operational range of NTM stabilisation in ASDEX Upgrade to lower q 95 and in the improved H-mode scenario. Our results suggest that for the ITER ECCD system, good localisation of the driven curent profile as well as the capability to modulate the ECCD in phase with rotating modes will be needed for efficient MHD control by ECCD.

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“…One possibility is that the asymptotic matching method does not apply for large ∆ . Another possibility is that quasi-linear stabilization terms play an important role [18]. These issues can only be resolved by performing nonlinear NTM simulations.…”

Section: Discussionmentioning

confidence: 99%

Modeling of neoclassical tearing mode stability for generalized toroidal geometry

et al. 2002

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Neoclassical tearing modes (NTMs) can lead to disruption and loss of confinement. Previous analysis of these modes used large aspect ratio, low β (plasma pressure/magnetic pressure) approximations to determine the effect of NTMs on tokamak plasmas. A more accurate tool is needed to predict the onset of these instabilities. As a follow-up to recent theoretical work, a code has been written which computes the tearing mode island growth rate for arbitrary tokamak geometry. It calls PEST-3 [A. Pletzer et al., J. Comput. Phys. 115, 530 (1994)] to compute Δ′, the resistive magnetohydrodynamic (MHD) matching parameter. The code also calls the FLUXGRID routines in NIMROD [A. H. Glasser et al., Plasma Phys. Controlled Fusion 41, A747 (1999)] for Dnc, DI, and DR [C. C. Hegna, Phys. Plasmas 6, 3980 (1999); A. H. Glasser et al., Phys. Fluids 18, 875 (1975)], which are the bootstrap current driven term and the ideal and resistive interchange mode criterion, respectively. In addition to these components, the NIMROD routines calculate αs–H, a new correction to the Pfirsch–Schlüter term. Finite parallel transport effects were added and a National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] equilibrium was analyzed. Another program takes the output of PEST-3 and allows the user to specify the rational surface, island width, and amount of detail near the perturbed surface to visualize the total helical flux. The results of this work will determine the stability of NTMs in a spherical torus (ST) [Y.-K. M. Peng et al., Nucl. Fusion 26, 769 (1986)] plasma with greater accuracy than previously achieved.

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Stabilization of neoclassical tearing modes using a continuous localized current drive

Cited by 73 publications

References 32 publications

Electron cyclotron current drive calculated for ITER conditions using different models

Electron cyclotron current drive calculated for ITER conditions using different models

Control of MHD instabilities by ECCD: ASDEX Upgrade results and implications for ITER

Modeling of neoclassical tearing mode stability for generalized toroidal geometry

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