Experiments on neoclassical tearing mode stabilization by ECCD in ASDEX Upgrade

Zohm, H.; Gantenbein, G.; Giruzzi, G.; Günter, S.; Leuterer, F.; Maraschek, M.; Meskat, J.; Peeters, A. G.; Suttrop, W.; Wágner, D.; Zabiégo, M.

doi:10.1088/0029-5515/39/5/101

Cited by 207 publications

(156 citation statements)

References 8 publications

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“…3 NTM suppression experiments have been performed successfully using both ECRH and ECCD. [4][5][6][7][8][9][10][11][12][13][14] The generalized Rutherford equation (GRE) 15,16 provides a theoretical model for the growth and stabilization of tearing modes. It describes the nonlinear temporal evolution of the full width w of the associated magnetic island as a function of different stabilizing and destabilizing mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Consequences of plasma rotation for neoclassical tearing mode suppression by electron cyclotron current drive

Ayten

Westerhof

2012

Physics of Plasmas

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In the generalized Rutherford equation describing the nonlinear evolution of the width of the magnetic island associated with a neoclassical tearing mode, the effect of localized current drive is represented by a term ΔCD′. We investigate oscillations in ΔCD′ originating from the rotation of the island through the electron cyclotron power deposition region and their dependence on the collisional time scale on which the driven current is generated, the rotation period, the island size, and the power deposition width. Furthermore, their consequences for the island growth or the stabilization are analyzed. This work shows that the net result of the oscillations in ΔCD′ is a slight increase in the stabilizing effect of electron cyclotron current drive and consequently, a reduction in the minimum power requirement to fully suppress an island.

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Section: Introductionmentioning

confidence: 99%

Consequences of plasma rotation for neoclassical tearing mode suppression by electron cyclotron current drive

Ayten

Westerhof

2012

Physics of Plasmas

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“…By the time of the previous review [5], the suppression of (m=3,n=2) NTMs had been demonstrated in several tokamaks [24], [25], [26] and [27] and first experiments on partial (2,1) suppression had been carried out. Also, first attempts at feedback control of the deposition had been made.…”

Section: Application Of Ecrh and Eccd For Optimization Of Plasma Stabmentioning

confidence: 99%

Recent Experimental Progress in Electron Cyclotron Resonance Heating and Electron Cyclotron Current Drive in Magnetically Confined Fusion Plasmas

Zohm

2007

Fusion Science and Technology

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A review of recent experimental results in the area of ECRH and ECCD is given. Special emphasis is put on the recent developments of new schemes in which EC waves can heat and drive current in magnetically confined fusion plasmas. These comprise scenarios to overcome the density cutoff experienced in application of the classical O1 and X2 scheme as well as to increase the current drive efficiency of EC waves while maintaining their good localization. In particular, we discuss recent experimental progress in tokamaks, stellarators and spherical tori in the areas of the O2, X3 and EBW schemes (mostly OXB scheme) as well as experiments in which the combination of ECCD with Lower Hybrid Current Drive (LHCD) leads to a synergetic increase of the ECCD efficiency. A particular application of ECCD that has recently received a lot of attention and is therefore reviewed in this paper is the suppression of Neoclassical Tearing Modes (NTMs) by ECCD. We show that the theoretically predicted requirements for ECCD in terms of deposition (maximising the ECCD driven current density) and injection in phase with the O-point of the magnetic island associated with the NTM (which is needed when the island width falls below the deposition width) have been verified experimentally. Also, many of the elements needed for constructing a reliable, feedback controlled NTM suppression system for ITER based on ECCD have now been demonstrated experimentally and the next step, which is their integration into a reliable scheme, is well within reach.

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“…In that respect, steady progress has been made at DIII-D, ASDEX-U, and JT60-U with regard to controlling NTMs using Electron Cyclotron Current Drive ͑ECCD͒. [37][38][39] For instance, the full suppression of magnetic islands has been achieved in some cases, with the added benefit that the plasma ␤ can be increased above the limiting instability threshold. Recent computational studies 8 have shown that a combined power of 25 MW might be required to control the 3 / 2 and 2 / 1 modes in ITER.…”

Section: -12mentioning

confidence: 99%

Integrated simulations of saturated neoclassical tearing modes in DIII-D, Joint European Torus, and ITER plasmas

Halpern¹,

Bateman²,

Kritz³

2006

Physics of Plasmas

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tokamak discharges in order to investigate the adverse effects of multiple saturated magnetic islands driven by neoclassical tearing modes ͑NTMs͒. Simulations are carried out with a predictive model for the temperature and density pedestal at the edge of the high confinement mode ͑H-mode͒ plasma and with core transport described using the Multi-Mode model. The ISLAND module, which is used to compute magnetic island widths, includes the effects of an arbitrary aspect ratio and plasma cross sectional shape, the effect of the neoclassical bootstrap current, and the effect of the distortion in the shape of each magnetic island caused by the radial variation of the perturbed magnetic field. Radial transport is enhanced across the width of each magnetic island within the BALDUR integrated modeling simulations in order to produce a self-consistent local flattening of the plasma profiles. It is found that the main consequence of the NTM magnetic islands is a decrease in the central plasma temperature and total energy. For the DIII-D and JET discharges, it is found that inclusion of the NTMs typically results in a decrease in total energy of the order of 15%. In simulations of ITER, it is found that the saturated magnetic island widths normalized by the plasma minor radius, for the lowest order individual tearing modes, are approximately 24% for the 2 / 1 mode and 12% for the 3 / 2 mode. As a result, the ratio of ITER fusion power to heating power ͑fusion Q͒ is reduced from Q = 10.6 in simulations with no NTM islands to Q = 2.6 in simulations with fully saturated NTM islands.

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Experiments on neoclassical tearing mode stabilization by ECCD in ASDEX Upgrade

Cited by 207 publications

References 8 publications

Consequences of plasma rotation for neoclassical tearing mode suppression by electron cyclotron current drive

Consequences of plasma rotation for neoclassical tearing mode suppression by electron cyclotron current drive

Recent Experimental Progress in Electron Cyclotron Resonance Heating and Electron Cyclotron Current Drive in Magnetically Confined Fusion Plasmas

Integrated simulations of saturated neoclassical tearing modes in DIII-D, Joint European Torus, and ITER plasmas

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