Fivefold confinement time increase in the Madison Symmetric Torus using inductive poloidal current drive

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

doi:10.1063/1.872324

Cited by 43 publications

(49 citation statements)

References 19 publications

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“…Therefore, a key to the future of the RFP as a magnetic confinement fusion reactor will be controlling or even eliminating the fluctuations that drive the dynamo. Progress towards this goal has been made in transient experiments in which the emf normally supplied by the dynamo is externally applied, 26 and plans have been made to extend this to steady-state current drive techniques. A rich area of future application of the measurement techniques described in this paper will be to examine the response of RFP plasma fluctuations to such current profile control.…”

Section: Understanding and Controlling The Dynamomentioning

confidence: 99%

Measurement of core velocity fluctuations and the dynamo in a reversed-field pinch

et al. 1999

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Section: Understanding and Controlling The Dynamomentioning

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Measurement of core velocity fluctuations and the dynamo in a reversed-field pinch

et al. 1999

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“…With the goal of modifying this gradient in Madison Symmetric Torus ͑MST͒ 2 reversedfield-pinch ͑RFP͒ plasmas, inductive auxiliary parallel current drive was applied at the plasma boundary. [3][4][5][6] Comprised of a poloidal electric field induced by a transient change in the toroidal flux in the plasma, this technique resulted in a reduction of the mϭ1 fluctuations and an increase in the global energy confinement time to 5 ms from the MST standard 1 ms.…”

Section: Introductionmentioning

confidence: 99%

High confinement plasmas in the Madison Symmetric Torus reversed-field pinch

et al. 2002

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Reduction of core-resonant mϭ1 magnetic fluctuations and improved confinement in the Madison Symmetric Torus ͓Dexter et al., Fusion Technol. 19, 131 ͑1991͔͒ reversed-field pinch have been routinely achieved through control of the surface poloidal electric field, but it is now known that the achieved confinement has been limited in part by edge-resonant mϭ0 magnetic fluctuations. Now, through refined poloidal electric field control, plus control of the toroidal electric field, it is possible to reduce simultaneously the mϭ0 and mϭ1 fluctuations. This has allowed confinement of high-energy runaway electrons, possibly indicative of flux-surface restoration in the usually stochastic plasma core. The electron temperature profile steepens in the outer region of the plasma, and the central electron temperature increases substantially, reaching nearly 1.3 keV at high toroidal plasma current ͑500 kA͒. At low current ͑200 kA͒, the total beta reaches 15% with an estimated energy confinement time of 10 ms, a tenfold increase over the standard value which for the first time substantially exceeds the constant-beta confinement scaling that has characterized most reversed-field-pinch plasmas.

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“…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%

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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Fivefold confinement time increase in the Madison Symmetric Torus using inductive poloidal current drive

Cited by 43 publications

References 19 publications

Measurement of core velocity fluctuations and the dynamo in a reversed-field pinch

Measurement of core velocity fluctuations and the dynamo in a reversed-field pinch

High confinement plasmas in the Madison Symmetric Torus reversed-field pinch

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

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