Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching

Fitzpatrick, Richard

doi:10.1063/1.4990701

Cited by 10 publications

(2 citation statements)

References 39 publications

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“…Linear simulations with β = 0.0016 (weakly stable), a (2, 1) error field, and plasma rotation Ω 0 verify that the largest response to the error field (peak reconnected flux) occurs near the phase velocity of the mode Ω r = ±ω r /m 4 . At the same time, the maximum response for β = 0 (near Ω 0 = 0) is strongly screened in the presence of GGJ propagation 3,4,12 . The present linear simulations also verify that the quasilinear Maxwell torque exerted by the error field on the tearing layer has a qualitatively different dependence 4 on the plasma rotation frequency from its β = 0 counterpart.…”

Section: Summary and Discussionmentioning

confidence: 96%

Nonlinear error field response in the presence of plasma rotation and real frequencies due to favorable curvature

et al. 2020

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We present nonlinear resistive MHD simulations of the response of a rotating plasma to an error field when the plasma has weakly damped linear tearing modes (TM's), stabilized by pressure gradient and favorable curvature. Favorable curvature leads to the Glasser effect: the occurrence of real frequencies and stabilization with positive stability index ∆ ′ . A cylinder with hollow pressure is used to model the toroidal favorable curvature. Linear simulations with rotation and an error fieldψ w show, in agreement with analytic results, that the peak reconnected flux occurs for a rotation rate near the TM phase velocity. Nonlinear simulations with smallψ w show that the real frequency and stabilization by favorable average curvature are masked by a nonlinear effect that occurs for very thin islands: flattening of the pressure across the island, mainly due to sound wave propagation. This flattening causes the disappearance of real frequencies destabilization of the mode, allowing it to grow to large amplitude similar to a =0 unstable TM. The flattening of the current for larger islands saturates the mode nonlinearly. In the post-saturation phase, the interaction of the error field with the destabilized spontaneous tearing mode, which rotates with the plasma, leads to oscillations in the Maxwell torque and therefore modulations in the plasma rotation. The islands also rotate with modulated phase velocity, undergoing small-amplitude oscillations due to these modulations. We also present a quasilinear model with an unstable spontaneous TM and error fields, showing that the superposition of these fields results in similar oscillations.

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Section: Summary and Discussionmentioning

confidence: 96%

Nonlinear error field response in the presence of plasma rotation and real frequencies due to favorable curvature

et al. 2020

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“…There are a number of improvements that could be made to the theory described in this paper. Such improvements include; 1) taking into account the coupling of different resonant surfaces via mode-penetration-induced changes in the plasma rotation, density, and temperature, profiles in the pedestal [18]; 2) taking into account the coupling of different poloidal harmonics of the RMP due to toroidicity, the Shafranov shift, and flux surface shaping [53]; 3) employing a more realistic plasma equilibrium; 4) including island saturation terms [54,55,56], the perturbed bootstrap current [57], and the perturbed ion polarization current [58], in the Rutherford equation; 5) taking into account orbit-squeezing effects due to the strong shear in the radial electric field that is typically present in H-mode tokamak pedestals [59]; 6) taking neoclassical toroidal flow-damping into account; 7) allowing for multiple impurity species; and 8) taking into account the fact that high-Z impurities can easily acquire supersonic neoclassical velocities [60].…”

Section: Discussionmentioning

confidence: 99%

Theory of edge localized mode suppression by static resonant magnetic perturbations in the DIII-D tokamak

Fitzpatrick

2020

Physics of Plasmas

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An analytic theory of edge localized mode (ELM) suppression in an H-mode tokamak plasma via the application of a static, externally generated, resonant magnetic perturbation (RMP) is presented. This theory is based on the plausible hypothesis that mode penetration at the top of the pedestal is a necessary and sufficient condition for the RMP-induced suppression of ELMs. The theory also makes use of a number of key insights gained in a recent publication (Fitzpatrick R 2019). The first insight is that the response of the plasma to a particular helical component of the RMP, in the immediate vicinity of the associated resonant surface, is governed by nonlinear magnetic island physics, rather than by linear layer physics. The second insight is that neoclassical effects play a vital role in the physics of RMP-induced ELM suppression. The final insight is that plasma impurities play an important role in the physics of RMPinduced ELM suppression. The theory presented in this paper is employed to gain a better understanding ELM suppression in DIII-D and ITER H-mode discharges. It is found that ELM suppression is only possible when q 95 takes values that lie in certain narrow windows. Moreover, the widths of these windows decrease with increasing plasma density. Assuming a core plasma rotation of 20 krad/s, the window width for a model ITER H-mode discharge is found to be similar to, but slightly smaller than, the window width in a typical DIII-D H-mode discharge.

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Two-fluid nonlinear theory of response of tokamak plasma to resonant magnetic perturbation

Fitzpatrick

2018

Physics of Plasmas

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A comprehensive two-fluid nonlinear theory of magnetic reconnection driven at a single, tearing-stable, rational surface embedded in an H-mode tokamak plasma is presented. The surface is assumed to be resonant with one of the dominant helical harmonics of an applied resonant magnetic perturbation (RMP). The theory described in this paper is highly relevant to the problem of understanding the physics of RMP-induced edge localized mode (ELM) suppression in tokamak plasmas.

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Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching

Cited by 10 publications

References 39 publications

Nonlinear error field response in the presence of plasma rotation and real frequencies due to favorable curvature

Nonlinear error field response in the presence of plasma rotation and real frequencies due to favorable curvature

Theory of edge localized mode suppression by static resonant magnetic perturbations in the DIII-D tokamak

Two-fluid nonlinear theory of response of tokamak plasma to resonant magnetic perturbation

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