Beyond the intelligent shell concept: the clean-mode-control

Zanca, P.; Marrelli, L.; Manduchi, G.; Marchiori, G.

doi:10.1088/0029-5515/47/11/004

Cited by 95 publications

(142 citation statements)

References 21 publications

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“…This is illustrated in Fig. 2, where the radial field is extrapolated at r = a by combining the radial and toroidal field measurements available at r = r wi [9]. The QSH brings a reduction of the global plasma stochasticity [13].…”

Section: The Clean Mode Controlmentioning

confidence: 97%

“…Formulas (4,5) are the standard vacuum solution for the radial magnetic field in terms of the modified Bessel Functions I p , K p , with the shell penetration described by the thin-shell dispersion relation [9]. In fact if M, N are large enough, the sidebands do not correspond to any unstable plasma mode and they can be estimated from the coils currents using the vacuum approximation [9].…”

Section: The Clean Mode Controlmentioning

confidence: 99%

“…In fact if M, N are large enough, the sidebands do not correspond to any unstable plasma mode and they can be estimated from the coils currents using the vacuum approximation [9]. In the IS scheme the feedback variables are the measurements b r i, j r related to the plasma perturbations: the sidebands p 0, or q 0 are computed in real-time from the coils currents using (4,5), and then subtracted in the expression (2) [9]. Of course, the aliasing effect in (2) can be reduced to negligible levels if the sensors and the active coils have very different periodicities in poloidal and toroidal directions.…”

Section: The Clean Mode Controlmentioning

confidence: 99%

“…This means that, in general, a feedback system cannot suppress the non-linear dynamo TMs, but at the best it can keep to low values their edge amplitudes. A recent upgrade of the intelligent shell developed in RFX-mod, the clean-mode-control (CMC) [9,10], leads to a better control of the TMs. In fact it fixes the TMs edge amplitudes at a lower level than the intelligent shell.…”

Section: Introductionmentioning

confidence: 99%

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Beyond the Intelligent-shell Concept: the Clean-mode-control for Tearing Perturbations

Zanca

2010

Plasma and Fusion Research

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The Intelligent Shell scheme, where a grid of active coils counteracts in a feedback scheme the measurements provided by an identical grid of sensors, has shown some limitations in the control of the dynamo tearing modes in RFX-mod. The origin of the problem is the aliasing on the measurements coming from the high periodicity sideband harmonics produced by the discrete nature of the active coils. A more efficient feedback on tearing modes is obtained by removing the sidebands from the measurements, thereby counteracting the true tearing Fourier modes. In this scheme, named Clean-Mode-Control, the sidebands are computed in real time from the coils currents using the cylindrical geometry approximation. The Clean-Mode-Control significantly alleviates the wall-locking of tearing modes in RFX-mod, giving the possibility of operating at a plasma current (1.5 MA) never reached before in a RFP machine. These features are well explained by a MHD model describing the tearing mode dynamic under the viscous torque due to the fluid motion and the electromagnetic torques produced by the feedback, the conductive structures surrounding the plasma and the non-linear interaction between the different modes [P. Zanca, Plasma Phys. Control. Fusion 51, No. 1, 015006 (2009)]. Here some new results obtained with this model are discussed. In particular we will show that the edge radial field control improves by reducing the ratio between the delay introduced by the digital acquisition of the measurements and the time constant of the shell that contains the plasma. In this formulation the active coils are assumed to be located outside the shell.

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Section: The Clean Mode Controlmentioning

confidence: 97%

Section: The Clean Mode Controlmentioning

confidence: 99%

Section: The Clean Mode Controlmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Beyond the Intelligent-shell Concept: the Clean-mode-control for Tearing Perturbations

Zanca

2010

Plasma and Fusion Research

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“…The traditional IS regulator [6] consequently drives the output to zero but does so happily ignorant of individual mode amplitudes. This is a fairly recent appreciation of the need for further development of control systems for MHD experiments [15], [14]. Indeed, IS operation typically excites higher mode numbers, which are, supposedly, stable and mainly transient.…”

Section: B Mimo Plant Modeling By Geometric Coupling Of Siso Dynamicsmentioning

confidence: 99%

Stability analysis and model-based control in EXTRAP-T2R with time-delay compensation

Olofsson¹,

Witrant

Briat

et al. 2008

2008 47th IEEE Conference on Decision and Control

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Abstract-In this paper, we investigate the stability problems and control issues that occur in a reversed-field pinch (RFP) device, EXTRAP-T2R (T2R), used for research in fusion plasma physics and general plasma (ionized gas) dynamics. The plant exhibits, among other things, magnetohydrodynamic instabilities known as resistive-wall modes (RWMs), growing on a time-scale set by a surrounding non-perfectly conducting shell. We propose a novel model that takes into account experimental constraints, such as the actuators dynamics and control latencies, which lead to a multivariable time-delay model of the system. The openloop field-error characteristics are estimated and a stability analysis of the resulting closed-loop delay differential equation (DDE) emphasizes the importance of the delay effects. We then design a structurally constrained optimal PID controller by direct eigenvalue optimization (DEO) of this DDE. The presented results are substantially based on and compared with experimental data.

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Flow Measurements in the Edge Region of the RFX‐Mod Experiment

Spolaore

Cavazzana

Innocente

et al. 2010

Contrib. Plasma Phys.

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In this contribution a detailed study of the edge flow properties performed on the outer region of the RFX-mod experiment using a Gundestrup probe is presented. In particular, both parallel and perpendicular components (with respect to the magnetic field) have been evaluated in several low current discharges providing a complete reconstruction of the edge flow profiles.Different methods based on both magnetized and unmagnetized models have been used to evaluate the averaged plasma flow components and their time variations. Furthermore, configurations involving either ion saturation current signals or floating potential ones have been used to evaluate both parallel and perpendicular flow components and a good agreement has been found between different methods.Finally, the dynamic behaviour of edge flow fluctuations induced by gradient modifications following pellet injection and by varying the edge magnetic topology (the m = 0 islands radial position) have been studied.

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Beyond the intelligent shell concept: the clean-mode-control

Cited by 95 publications

References 21 publications

Beyond the Intelligent-shell Concept: the Clean-mode-control for Tearing Perturbations

Beyond the Intelligent-shell Concept: the Clean-mode-control for Tearing Perturbations

Stability analysis and model-based control in EXTRAP-T2R with time-delay compensation

Flow Measurements in the Edge Region of the RFX‐Mod Experiment

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