Tearing mode analysis in tokamaks, revisited

Nishimura, Y.; Callen, J. D.; Hegna, C. C.

doi:10.1063/1.873166

Cited by 27 publications

(49 citation statements)

References 19 publications

(19 reference statements)

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“…The shift in the peak of the parallel vector potential with respect to the cylindrical calculation is consistent with previous work performed using an ideal MHD code. 11 Plotted is also the radial eigenfunction for a simulation using an aspect ratio of R/a ¼ 10, closer to the cylindrical limit, which shows that the eigenfunction tends toward this cylindrical form as expected. The radial equilibrium ion and electron density, safety factor and magnetic shear profiles used are shown in the second (upper middle) panel.…”

Section: Parametersmentioning

confidence: 50%

“…6 The tearing mode can trigger a disruption, something which would be catastrophic to the ITER tokamak and therefore the tearing mode, and specifically, the neoclassical tearing mode (NTM) [7][8][9] is expected to be the limiting factor on its operational plasma b. 10 Much work has been performed numerically in studying tearing mode stability in both cylindrical and toroidal geometry, 11 using the magnetohydrodynamic (MHD) framework. However, for large current and future tokamaks, a fully kinetic description of the physics in the resonant layer is needed for both the linear and non-linear regimes.…”

Section: Introductionmentioning

confidence: 99%

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The linear tearing instability in three dimensional, toroidal gyro-kinetic simulations

et al. 2015

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Linear gyro-kinetic simulations of the classical tearing mode in three-dimensional toroidal geometry were performed using the global gyro-kinetic turbulence code, GKW. The results were benchmarked against a cylindrical ideal MHD and analytical theory calculations. The stability, growth rate, and frequency of the mode were investigated by varying the current profile, collisionality, and the pressure gradients. Both collisionless and semi-collisional tearing modes were found with a smooth transition between the two. A residual, finite, rotation frequency of the mode even in the absence of a pressure gradient is observed, which is attributed to toroidal finite Larmor-radius effects. When a pressure gradient is present at low collisionality, the mode rotates at the expected electron diamagnetic frequency. However, the island rotation reverses direction at high collisionality. The growth rate is found to follow a g 1=7 scaling with collisional resistivity in the semi-collisional regime, closely following the semi-collisional scaling found by Fitzpatrick. The stability of the mode closely follows the stability analysis as performed by Hastie et al. using the same current and safety factor profiles but for cylindrical geometry, however, here a modification due to toroidal coupling and pressure effects is seen. V C 2015 AIP Publishing LLC. [http://dx.

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Section: Parametersmentioning

confidence: 50%

Section: Introductionmentioning

confidence: 99%

The linear tearing instability in three dimensional, toroidal gyro-kinetic simulations

et al. 2015

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“…54,55 The ⌬Ј code solves the tearing mode equation for the perturbed helical flux function ⌿ in cylindrical tokamak geometry, 94 and therefore, the analysis may be considered to yield an estimate of the lower stability limit, since stabilizing effects due to toroidal geometry effects and pressure induced curvature effects are neglected. 95 The tearing mode stability index ⌬Ј, with ⌬ЈϾ0 in the unstable case, denotes the discontinuity of ⌿Ј/⌿ across the resonant surface and is sensitive to the local current gradient. The external helical field does not directly enter into the stability calculation but only through the iota profile.…”

Section: B Stability Analysismentioning

confidence: 99%

Survey of magnetohydrodynamic instabilities in the advanced stellarator Wendelstein 7-AS

et al. 2001

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Magnetohydrodynamic (MHD) instabilities in the Wendelstein 7-AS stellarator (W7-AS) [G. Grieger et al., Phys. Fluids B 4, 2081 (1992)] are characterized experimentally in various plasma parameter regimes and heating scenarios. The observations are compared with theoretical predictions for particular cases. In the high-β range (〈β〉⩽2%) no clear evidence of a stability β-limit could be found yet. In the lower β regime fast particle driven global Alfvén modes are the most important instabilities during neutral beam injection (NBI). Besides of coherent modes with almost no effect on the plasma performance additional Alfvén modes appear at higher frequencies up to 400 kHz, which show nonlinear phenomena-like bursting, frequency chirping, and MHD induced energy and fast particle losses. The activity of edge localized modes (ELMs) is investigated in NBI heated discharges. The issue of current driven instabilities and their potential stabilization by a stellarator field has been investigated with regard to the design of compact hybrid stellarator systems.

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“…The tearing mode can lead to the deterioration of the confinement, mode locking to the external resistive wall, and plasma disruption. [1][2][3] The onset of the neoclassical tearing mode (NTM) provides a limitation for achievable b (the ratio of the averaged plasma pressure to the magnetic pressure). It is known that the favorable averaged curvature of the equilibrium magnetic field has strong stabilization effect on the tearing mode.…”

Section: Introductionmentioning

confidence: 99%

Resistive wall tearing mode generated finite net electromagnetic torque in a static plasma

et al. 2014

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The MARS-F code [Y. Q. Liu et al., Phys. Plasmas 7, 3681 (2000)] is applied to numerically investigate the effect of the plasma pressure on the tearing mode stability as well as the tearing mode-induced electromagnetic torque, in the presence of a resistive wall. The tearing mode with a complex eigenvalue, resulted from the favorable averaged curvature effect [A. H. Glasser et al., Phys. Fluids 18, 875 (1975)], leads to a re-distribution of the electromagnetic torque with multiple peaking in the immediate vicinity of the resistive layer. The multiple peaking is often caused by the sound wave resonances. In the presence of a resistive wall surrounding the plasma, a rotating tearing mode can generate a finite net electromagnetic torque acting on the static plasma column. Meanwhile, an equal but opposite torque is generated in the resistive wall, thus conserving the total momentum of the whole plasma-wall system. The direction of the net torque on the plasma is always opposite to the real frequency of the mode, agreeing with the analytic result by Pustovitov [Nucl. Fusion 47, 1583(2007]. When the wall time is close to the oscillating time of the tearing mode, the finite net torque reaches its maximum. Without wall or with an ideal wall, no net torque on the static plasma is generated by the tearing mode. However, re-distribution of the torque density in the resistive layer still occurs. V C 2014 AIP Publishing LLC.

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Tearing mode analysis in tokamaks, revisited

Cited by 27 publications

References 19 publications

The linear tearing instability in three dimensional, toroidal gyro-kinetic simulations

The linear tearing instability in three dimensional, toroidal gyro-kinetic simulations

Survey of magnetohydrodynamic instabilities in the advanced stellarator Wendelstein 7-AS

Resistive wall tearing mode generated finite net electromagnetic torque in a static plasma

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