Feedback Control of Major Disruptions in Tokamaks

Sen, Abhijit

doi:10.1103/physrevlett.76.1252

Cited by 11 publications

(14 citation statements)

References 9 publications

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“…9,10 The basic mechanism is the injection of time varying ͑at the instability frequency͒ radial momentum of appropriate amplitude and phase via a feedback loop. We have now clarified the physics of the absorption of the radial momentum by the plasma both in terms of an ideal MHD fluid and a particle picture.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…9, where an additional state was generated via differentiation of the sensor output signal. In an experiment involving stabilization of two electrostatic modes in the Columbia Linear Machine the same simple philosophy of generation of extra states via differentiation was used successfully.…”

Section: Multimode Feedback "Practical…mentioning

confidence: 99%

“…8 One reason for this relative lack of present and possibly future success may be due to inadequate coupling to more internal type modes (mϭ3, nϭ2 and certainly mϭ1, nϭ1), because of the surface current nature of the suppressor signal. We address this problem by using the recently proposed neutral beam suppressor, 9 which can inject the control signal deep into the plasma where the modes are located. This may be an attractive possibility as neutral beams will probably continue to be used in large tokamaks for auxiliary heating.…”

Section: Introductionmentioning

confidence: 99%

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Feedback control of multimode magnetohydrodynamic instabilities via neutral beams

Sen

1998

Physics of Plasmas

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Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Multimode Feedback "Practical…mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Feedback control of multimode magnetohydrodynamic instabilities via neutral beams

Sen

1998

Physics of Plasmas

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“…[12][13][14][15] However, neutral beam suppressors may have some advantages, especially when the modes are located deep in the plasma, e.g., a mϭ1, nϭ1 MHD mode. The stabilization of a single ideal MHD mode (mϭ2,nϭ1) 16 or a single tearing mode (mϭ1,nϭ1) 17 via a neutral beam suppressor has been discussed before. However, when one mode is stabilized another mode is often destabilized, 18,19 as mentioned before.…”

Section: Control Of Multimode Mhd Instabilities Via Neutral Beam mentioning

confidence: 99%

Control and diagnostic uses of feedback

Sen

2000

Physics of Plasmas

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Recent results on multimode feedback control of magnetohydrodynamic (MHD) modes and a variety of diagnostic uses of feedback are summarized. First, is the report on reduction and scaling of transport under feedback. By controlling the fluctuation amplitudes and consequently the transport via feedback, it is found that the scaling of the diffusion coefficient is linear with root-mean-square rms fluctuation level. The scaling appears not to agree with any generic theory. A variety of other diagnostic uses of feedback have been developed. The primary goal is an experimental methodology for the determination of dynamic models of plasma turbulence, both for better transport understanding and more credible feedback controller designs. A specific motivation is to search for a low-order dynamic model, suitable for the convenient study of both transport and feedback. First, the time series analysis method is used for the determination of chaotic attractor dimension of plasma fluctuations. For E×B rotational flute modes it is found to be close to three, indicating that a low-order dynamic model may be adequate for transport prediction and feedback controller design. Second, a new method for direct experimental determination of nonlinear dynamical models of plasma turbulence using feedback has been developed. Specifically, the process begins with a standard three-wave coupling model and introduces a variable feedback gain. The power spectrum, delayed power spectrum, and bispectrum of fluctuations are then experimentally obtained. By varying the feedback gain continuously, an arbitrary number of numerical equations for a fixed number of unknowns can be generated. Their numerical solution yields the linear dispersion, as well as nonlinear coupling coefficients. This method has been successfully applied for E×B rotationally driven flute modes.

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“…Drift-wave turbulence is generally believed to be responsible for the anomalous crossfield particle transport [23], and its control and suppression therefore is of great importance to the performance of magnetic confinement fusion devices, e.g., the tokamaks [24]. Over * Corresponding author: wangxg@snnu.edu.cn the past two decades, there have been continuous attempts in extending the techniques developed in chaos control to the suppression of drift-wave turbulence, in which a variety of theories and techniques have been proposed [25][26][27][28][29][30][31][32]. In the regime of weak turbulence, by use of the technique of timedelay autosynchronization (TDAS) [33], it has been shown by a series of studies that the chaotic temporal behavior of the drift waves in cylindrical magnetized plasmas can be tamed to be periodic [25,27,31].…”

Section: Introductionmentioning

confidence: 99%

Network approach to the pinning control of drift-wave turbulence

Deng

Yang

et al. 2014

Phys. Rev. E

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Network of coupled oscillators has long been employed as an important approach to explore the complicated dynamics in spatially extended systems. Here we show how this approach can be used to the analysis of turbulence pinning control. Specifically, by use of a model of two-dimensional drift-wave plasma turbulence, we investigate how the performance of the turbulence control is influenced by the spatial distribution of the pinning strength. It is found that the dynamics of pinned turbulence can be well captured by a simple model of networked modes, based on which the dependence of the control performance on the pinning distribution can be analytically obtained. In particular, the model predicts that as the distribution of the pinning strength becomes more nonuniform, the performance of turbulence control will be gradually decreased. This theoretical prediction is in good agreement with the results of numerical simulations, including the sinusoidal and localized pinning distributions. Our studies provide a new viewpoint to the mechanism of mode couplings in drift-wave turbulence, as well as be constructive to the design of new schemes for controlling turbulence in realistic systems.

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Feedback Control of Major Disruptions in Tokamaks

Cited by 11 publications

References 9 publications

Feedback control of multimode magnetohydrodynamic instabilities via neutral beams

Feedback control of multimode magnetohydrodynamic instabilities via neutral beams

Control and diagnostic uses of feedback

Network approach to the pinning control of drift-wave turbulence

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