Increased Confinement and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">β</mml:mi></mml:math>by Inductive Poloidal Current Drive in the Reversed Field Pinch

Sarff, J. S.; Lanier, N. E.; Prager, S. C.; Stoneking, M. R.

doi:10.1103/physrevlett.78.62

Cited by 112 publications

(113 citation statements)

References 21 publications

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“…The results of calculation correspond to S = 10 6 and two values of applied electric field are considered, E h 1 = 0.3 V/m, E h 2 = 0.6 V/m. These electric fields are comparable with the ones driven in the experiment and the magnetic field reversal at the end of the drive calculated with these fields is comparable to the experimentally observed one as well.…”

Section: Resultsmentioning

confidence: 99%

“…Initial plasma resistivity profile is g = g 0 [1 + 4(r/r p ) 6 ]. We specify its time evolution as dg/dt = 0.…”

Section: Model Descriptionmentioning

confidence: 99%

“…In the current-drive technique, called pulsed poloidal current drive (PPCD), a poloidal (parallel) electric field is induced by transiently increasing the reversed toroidal magnetic flux in the edge [5][6][7][8][9]. In the MST RFP this auxiliary current drive reduces magnetic and electrostatic fluctuations everywhere in the plasma and significantly improves plasma confinement [10].…”

Section: Introductionmentioning

confidence: 99%

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On the Physics of Improved Confinement During Pulsed Poloidal Current Drive in MST Reversed-Field Pinch

Svidzinski

Prager

2006

J Fusion Energ

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Reduction of core-resonant magnetic fluctuations and improved confinement in the Madison Symmetric Torus reversed-field pinch (MST RFP) have been routinely achieved by applying the surface poloidal electric field. The created inductive poloidal electric field drives current in plasma which leads to the improved confinement. To study the effect we developed a relatively simple 1-D model in cylindrical geometry which assumes poloidal and axial symmetry during the drive. We use resistive magnetohydrodynamics model with realistic plasma parameters and assume that there is a vacuum gap between plasma boundary and conducting wall of the vessel. Evolution of plasma density is taken into account and plasma boundary moves selfconsistently with momentum equation. We start from an initial unstable equilibrium and examine stability of plasma configuration at intermediate moments of time during the drive. For this we calculate the growth rates of unstable eigenmodes in the plasma. Our results show that the modifications to the plasma current profile during the drive are stabilizing. The initial stabilization is due to the direct modification of the current profile near the edge. It enhances later in time due to the flattening of k profile in the core region as plasma and magnetic field compress inward during the drive.

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Section: Resultsmentioning

confidence: 99%

“…Initial plasma resistivity profile is g = g 0 [1 + 4(r/r p ) 6 ]. We specify its time evolution as dg/dt = 0.…”

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the Physics of Improved Confinement During Pulsed Poloidal Current Drive in MST Reversed-Field Pinch

Svidzinski

Prager

2006

J Fusion Energ

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“…3 In this paper we examine the behavior of the linear resistive interchange instability in current-carrying cylindrical plasmas, as beta varies from less than the ideal stability ͑Suy-dam͒ limit to much larger than the ideal limit.…”

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confidence: 99%

“…2 In the RFP, control of the current density profile has succeeded in substantially reducing currentdriven tearing instability and increasing beta to the point that pressure-driven modes may begin to be consequential. 3 In this paper we examine the behavior of the linear resistive interchange instability in current-carrying cylindrical plasmas, as beta varies from less than the ideal stability ͑Suy-dam͒ limit to much larger than the ideal limit.…”

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confidence: 99%

Resistive–ideal transition of pressure-driven instabilities in current-carrying plasmas beyond the Suydam criterion

2002

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The linear magnetohydrodynamics stability of local and global resistive pressure-driven instabilities is examined computationally in a cylinder. Both instabilities are resistive from beta values of zero up to several times the Suydam limit. Both transition to ideal modes at higher beta values. No sudden change in growth rate occurs at the Suydam limit. The global pressure-driven modes, of tearing parity, will likely be important in high beta plasmas, such as obtained in the reversed field pinch. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1481860͔The linear stability of ideal and resistive pressure-driven interchange modes is an old subject that has received extensive analysis. Its relevance today is somewhat heightened, as experiments with unfavorable magnetic curvature, such as reversed field pinches ͑RFP͒ and stellarators, are operating with pressure at or above the ideal interchange stability limit. In stellarators beta values above the Mercier limit are obtained in experiment, with no observation of instability.1 The investigation of global resistive modes have been examined in stellarators in currentless equilibria applicable to the Heliotron DR device.2 In the RFP, control of the current density profile has succeeded in substantially reducing currentdriven tearing instability and increasing beta to the point that pressure-driven modes may begin to be consequential. 3 In this paper we examine the behavior of the linear resistive interchange instability in current-carrying cylindrical plasmas, as beta varies from less than the ideal stability ͑Suy-dam͒ limit to much larger than the ideal limit.The ideal interchange instability in a cylinder has been examined in some detail, following the calculation by Suydam that a localized pressure-driven instability in a bad curvature region, is excited if the stability parameter D S ϭϪ(8pЈ/r)(q/B z qЈ) 2 ͉ r s Ͼ0.25, 4 where q is the safety factor, p is the pressure and ( )Јϭd/dr. Subsequently, the dependence of the analytic growth rate on D S ͑in the limit of large wave number, k͒ has been treated by several authors. 5,6 In many of these treatments the inertial term is included in a layer around the resonant surface only. The eigenfunction solution in the outer region is matched to that obtained in the layer. [7][8][9] The result is that the growth rate depends on D S ͑which is proportional to beta͒ as ␥ max ϷC exp (Ϫ2/ͱ), where ϭD S Ϫ0.25. Thus, the growth rate is exponentially small near the ideal limit (D S ϭ0.25), becoming large for D S values well above this limit. Numerical values for the growth rate of ideal interchange modes have also been obtained in a diffuse linear pinch. 10,11

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Reversed Field Pinch

Miyamoto¹

2016

Plasma Physics for Controlled Fusion

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Increased Confinement andβby Inductive Poloidal Current Drive in the Reversed Field Pinch

Cited by 112 publications

References 21 publications

On the Physics of Improved Confinement During Pulsed Poloidal Current Drive in MST Reversed-Field Pinch

On the Physics of Improved Confinement During Pulsed Poloidal Current Drive in MST Reversed-Field Pinch

Resistive–ideal transition of pressure-driven instabilities in current-carrying plasmas beyond the Suydam criterion

Reversed Field Pinch

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