RFP stability with a resistive shell in HBTX1C

Alper, B.; Bevir, M. K.; Bodin, H.A.B.; Bunting, C. A.; Carolan, P. G.; Cunnane, J; Evans, D.E.; Gimblett, C. G.; Hayden, Richard J.; Hender, T. C.; Lazaros, A.; Moses, R.W.; Newton, A.A.; Noonan, P.; Paccagnella, R.; Patel, A.; Tsui, H.Y.W.; Wilcock, P.

doi:10.1088/0741-3335/31/2/006

Cited by 95 publications

(71 citation statements)

References 6 publications

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“…[3][4][5][6][7][8][9][10][11] In RFPs, apart from the first observation of RWM reported in HTBX1C in 1988, 12 numbers of studies have been reported in recent years, both experimentally and theoretically; [13][14][15][16][17][18][19] in particular, the successful feedback control of multiple unstable RWMs has shown to be achieved by the equipments implemented in the experiments. [17][18][19] For instance, in RFX-mod 20 experiments, the observations give an evidence that the system of the active control has a sufficient efficiency and a large flexibility 18 and therefore can provide an excellent environment to apply and/or to test RWM physical modeling and various control scenarios, 21 which can further provide a better understanding for RWM physics and the control strategy.…”

Section: Introductionmentioning

confidence: 99%

Comparison between cylindrical model and experimental observation on the study of resistive wall mode in reversed field pinch plasmas

et al. 2010

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A cylindrical magnetohydrodynamic model including plasma pressure and longitudinal flow has been employed for the study of resistive wall mode ͑RWM͒ in reversed field pinch ͑RFP͒ plasmas. In order to validate the model, a careful comparison with the experimental measurements in RFX-mod ͓P. Sonato et al., Fusion Eng. Des. 66-68, 161 ͑2003͔͒ on the mode growth rates has been made by well matching the equilibrium parameters F, ⌰, and ␤ p . The RWM instability spectrum, which varies with the equilibrium parameters, is also calculated for comparison. The sensitivity of the mode growth rate to the equilibrium parameters is studied in details. It is concluded that the model can provide consistent accuracy in studies of RWM in RFP plasmas. The analysis based on the balance of the potential energy components has been carried out in order to obtain the physical understanding on the mode behavior.

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Section: Introductionmentioning

confidence: 99%

Comparison between cylindrical model and experimental observation on the study of resistive wall mode in reversed field pinch plasmas

et al. 2010

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“…RFX-mod has demonstrated the possibility to overcome these limitations with the active control of the edge radial field, made possible by a grid of active coils, placed outside the shell, fully covering the torus. The first scheme tested, the so-called intelligent-shell (IS) [4], in which the coils are coupled in a feedback scheme with the measurements provided by an identical grid of radial field sensors, improves the plasma performances by preventing the radial field penetration of the shell [5]: besides a complete suppression of the resistive wall modes [6], the TMs edge amplitude is kept at a low value. In RFPs TMs in the non-linear regime are required by the dynamo mechanism in order to maintain the reversed configuration [7,8].…”

Section: Introductionmentioning

confidence: 99%

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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“…The RWM has been identified in a number of devices. 9,10 The advanced tokamak program is addressing means by which to stabilize the RWM by using active methods to control the plasma rotation, 11 and by using feedback with magnetic coils. [12][13][14] The Gimblett double wall configuration does not require active means to suppress an instability.…”

Section: Introductionmentioning

confidence: 99%

Stabilization of line tied resistive wall kink modes with rotating walls

Hegna

2004

Physics of Plasmas

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A method suggested by Gimblett [ C. G. Gimblett, Plasma Phys. Controlled Fusion, 31 2183 (1989) ] for stabilizing resistive wall modes by using a rotating double wall configuration is applied to a line tied screw pinch equilibrium. The line tied boundary conditions provide an additional stabilizing mechanism relative to instabilities present in periodic cylinders that limits ideal kink instability to only be present when qa<1 for m=1 modes. With differentially rotating walls, resistive wall modes can be stabilized with qa values less than unity. For a given equilibrium, there exists an optimal spacing between a stationary and a rotating wall that minimizes the critical wall rotation frequency for stabilization.

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RFP stability with a resistive shell in HBTX1C

Cited by 95 publications

References 6 publications

Comparison between cylindrical model and experimental observation on the study of resistive wall mode in reversed field pinch plasmas

Comparison between cylindrical model and experimental observation on the study of resistive wall mode in reversed field pinch plasmas

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

Stabilization of line tied resistive wall kink modes with rotating walls

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