High-β, improved confinement reversed-field pinch plasmas at high density

Wyman, Max; Chapman, B.E.; Ahn, J.-W.; Almagri, A. F.; Anderson, J. K.; Bonomo, F.; Brower, D. L.; Combs, S. K.; Craig, D.; Hartog, D. J. Den; Deng, B. H.; Ding, W. X.; Ebrahimi, F.; Ennis, D.A.; Fiksel, G.; Foust, C. R.; Franz, P.; Gangadhara, S.; Goetz, J. A.; O’Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J.A.; Sarff, J. S.; Stephens, H.D.; Yates, T.

doi:10.1063/1.2835439

Cited by 19 publications

(21 citation statements)

References 26 publications

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“…Research on Reversed Field Pinch (RFP) configurations has experienced in the recent years substantial progress [Marrelli 2007, Wyman 2008, Brunsell 2006, Hirano 2006, with significant advances both in terms of plasma performance and control, and of understanding of relevant physics. The aim of this paper is to add to the line of such progress new interesting physics results, which are emerging from the reliable operation of RFX-mod in the regime with plasma current above 1 MA.…”

Section: Introductionmentioning

confidence: 99%

High current regimes in RFX-mod

Valisa

Bolzonella

Buratti

et al. 2008

Plasma Phys. Control. Fusion

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Abstract.Optimization of machine operation, including plasma position control, density control, and especially feedback control on multiple magnetohydrodynamic modes has led RFX-mod to reliably operate at 1.5 MA, the highest current ever achieved on a Reversed Field Pinch (RFP). At high current and low density the magnetic topology spontaneously self-organizes in an Ohmical helical symmetry, with the new magnetic axis helically twisting around the geometrical axis of the torus. The separatrix of the island disappears leaving a wide and symmetric thermal structure with large gradients in the electron temperature profile. The new topology still displays an intermittent nature but its overall presence has reached 85 % of the current flat top period. The large gradients in the electron temperature profile appear to be marginal for the destabilization of Ion Temperature Gradient modes on the assumption that ions and electrons have the same gradients. There are indications that higher currents could provide the conditions where to prove the existence of a true helical equilibrium as the standard RFP configuration

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Section: Introductionmentioning

confidence: 99%

High current regimes in RFX-mod

Valisa

Bolzonella

Buratti

et al. 2008

Plasma Phys. Control. Fusion

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“…Recent experiments in MST succeeded in achieving a maximum β p of 40% by using PPCD in combination with a pellet injection technique, with an energy confinement time of ∼ 5 ms; this represents a five-fold improvement in confinement compared to the standard case [11]. It can be estimated that electrons contributed about half of the β p .…”

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confidence: 99%

Electron Temperature Measurement by Thomson Scattering in a Low-Aspect-Ratio RFP RELAX

Ueba

Masamune

Sanpei

et al. 2014

Plasma and Fusion Research

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A Thomson scattering diagnostic system has been developed for measuring electron temperatures in lowaspect-ratio reversed-field pinch (RFP) plasmas in REversed-field pinch of Low Aspect ratio eXperiment (RE-LAX). In the range of plasma currents I p = 50 -80 kA, the central electron temperature was around 100 eV and, showed a weakly increasing trend as I p increases. To estimate the central electron pressure p e0 , a density calibration was performed from simultaneous measurements with a 104-GHz microwave interferometer. The maximum p e0 increased with I p up to ∼ 70 kA to preserve the approximate relation p e0 /B θa 2 ∼ constant, where B θa is the edge poloidal field. In the higher current region, p e0 tended to saturate, which may be improved by optimizing minute control of equilibrium in the higher current region.

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“…Single helicity (SH) or quasisingle helicity (QSH) states are believed to provide a better confinement with respect to turbulent RFP configurations. Experimental studies have shown the improvement in confinement associated with the presence of QSH states [6][7][8].…”

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confidence: 99%

Compressibility Effects in the Dynamics of the Reversed-Field Pinch

2008

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We study the reversed-field pinch through the numerical solution of the compressible magnetohydrodynamic equations. Two cases are investigated: In the first case the pressure is derived from an adiabatic condition, and in the second case the pressure equation includes heating terms due to resistivity and viscosity. In the adiabatic case a single helicity state is observed, and the reversed-field pinch configuration is formed for short time intervals and is finally lost. In the nonadiabatic case the system reaches a multiple helicity state, and the reversal parameter remains negative for a longer time. The results show the importance of compressibility in determining the large scale dynamics of the system.

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High-β, improved confinement reversed-field pinch plasmas at high density

Cited by 19 publications

References 26 publications

High current regimes in RFX-mod

High current regimes in RFX-mod

Electron Temperature Measurement by Thomson Scattering in a Low-Aspect-Ratio RFP RELAX

Compressibility Effects in the Dynamics of the Reversed-Field Pinch

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