Reduced Edge Instability and Improved Confinement in the MST Reversed-Field Pinch

Chapman, B.E.; Anderson, J. K.; Biewer, T. M.; Brower, D. L.; Castillo, S.; Chattopadhyay, Pratip K.; Chiang, C. S.; Craig, D.; Hartog, D. J. Den; Fiksel, G.; Fontana, P. W.; Forest, C. B.; Gerhardt, S. P.; Hansen, A. K.; Holly, D. J.; Jiang, Yong; Lanier, N. E.; Prager, S. C.; Reardon, J. C.; Sarff, J. S.

doi:10.1103/physrevlett.87.205001

Cited by 73 publications

(37 citation statements)

References 17 publications

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“…Recently, energy loss in RFP experiments has been reduced tenfold through modification of the current density profile, the source of the free energy for the tearing instabilities [3,4]. It has been conjectured that the improved confinement of the bulk plasma energy results from reduction of the magnetic stochasticity.…”

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confidence: 99%

Observation of Velocity-Independent Electron Transport in the Reversed Field Pinch

et al. 2003

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Confinement of runaway electrons has been observed for the first time in a reversed field pinch during improved-confinement plasmas in the Madison Symmetric Torus. Energy-resolved hard-x-ray flux measurements have been used to determine the velocity dependence of the electron diffusion coefficient, utilizing computational solutions of the Fokker-Planck transport equation. With improved-confinement, the fast electron diffusivity drops by 2 orders of magnitude and is independent of velocity. This suggests a change in the transport mechanism away from stochastic magnetic field diffusion.

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confidence: 99%

Observation of Velocity-Independent Electron Transport in the Reversed Field Pinch

et al. 2003

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“…These magnetic fluctuations are reduced when parallel current drive is added in the edge of a standard RFP plasma [1]. Recent inductive current drive experiments on MST [2] have produced a nine-fold improvement in the energy confinement, a tripling of the electron temperature, and a doubling of beta [3]. However, inductive current drive is an inherently transient technique and is non-local in nature.…”

Section: Introductionmentioning

confidence: 94%

Lower Hybrid Experiments in MST

Kaufman¹,

Goetz²,

Burke³

2003

AIP Conference Proceedings

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Current drive using RF waves has been proposed as a means to reduce the tearing fluctuations responsible for anomalous energy transport in the RFP. A traveling wave antenna that operates at 800 MHz is being used to launch lower hybrid waves into MST to assess the feasibility of this approach. The power flowing through the antenna has been measured with pickup loops installed in the antenna backplane. The measured power damping length of 2-4 parallel wavelengths is consistent with analytic calculations. The damping length decreases with increasing plasma density and increases in improved confinement discharges. Localized hard x-ray emission has been observed when energy flows in either direction through the antenna.

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“…The topic of stochastic magnetic field lines in fusion plasmas has been investigated for many years: in tokamaks [3][4][5][6], stellarators [7,8] and reversed field pinch (RFP) experiments [9]. In the ideal case all the tokamak experiments assume the magnetic flux surfaces start with a nested (onion skin) axisymmetric topology before the non-axisymmetric magnetic perturbation is applied.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Resonant Magnetic Perturbation on the Plasma Boundary in DIII‐D

Jakubowski

Evans

Fenstermacher

et al. 2010

Contrib. Plasma Phys.

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Stochastic boundaries in fusion devices have been investigated in tokamaks, stellarators and reversed field pinch experiments for many years. However, since edge localized modes (ELMs) have been successfully eliminated in H-mode plasmas at the DIII-D tokamak [1, 2] with small, edge resonant magnetic perturbations, they have become a widely investigated topic in tokamaks. In DIII-D stochastic boundaries are produced by coils external to the plasma. The magnetic field there consists of field lines with very different connection lengths, which produces a three dimensional, heterogenous structure of stochastic volume. The most obvious manifestation of the perturbed plasma edge is the strike line splitting observable in heat and particle fluxes, which changes with collisionality. The interaction of the magnetic perturbation and the magnetic equilibrium is of a resonant nature and the structure of the stochastic volume is a strong function of q95. This is observed as a modulation of e.g. electron temperature as measured by ECE or Thomson scattering. In this work we summarize recent experimental findings on properties of the stochastic boundary in DIII-D.

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Reduced Edge Instability and Improved Confinement in the MST Reversed-Field Pinch

Cited by 73 publications

References 17 publications

Observation of Velocity-Independent Electron Transport in the Reversed Field Pinch

Observation of Velocity-Independent Electron Transport in the Reversed Field Pinch

Lower Hybrid Experiments in MST

Influence of the Resonant Magnetic Perturbation on the Plasma Boundary in DIII‐D

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