Filamentary current structures in the Madison Symmetric Torus

Piovesan, P.; Almagri, A. F.; Chapman, B.E.; Craig, D.; Marrelli, L.; Martin, P.; Prager, S. C.; Sarff, J. S.

doi:10.1088/0029-5515/48/9/095003

Cited by 8 publications

(10 citation statements)

References 28 publications

(60 reference statements)

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“…The EC periods in MST are characterized in part by regularly occurring bursts of m = 0 mode activity. Each burst causes a temporary degradation of confinement [57]. Such bursts can also occur in PPCD plasmas, with a similar effect on confinement [319].…”

Section: Other Routes To Improved Confinementmentioning

confidence: 83%

“…The generation of the toroidal flux is a local, toroidally asymmetric phenomenon as a consequence of the nonlinear phase alignment [54]. Toroidally localized, magnetic field aligned current sheets have been measured in RFX-mod [55] and in MST [56,57].…”

Section: Multiple Helicity Regimementioning

confidence: 99%

“…The physics of these spontaneous periods of improved confinement, and the m = 0 bursts occurring in EC and PPCD plasmas in MST, is not well understood. However, based on the fact that the bursts bear some resemblance to edge-localized modes in tokamak H-mode plasmas [57,456], it was hypothesized that E × B flow shear could play a role. In the PPCD case, this would not be overly surprizing given the emergence of tokamak-like microinstabilities.…”

Section: Other Routes To Improved Confinementmentioning

confidence: 99%

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The reversed field pinch

et al. 2021

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This paper reviews the research on the reversed field pinch (RFP) in the last three decades. Substantial experimental and theoretical progress and transformational changes have been achieved since the last review (Bodin 1990 Nucl. Fusion 30 1717–37). The experiments have been performed in devices with different sizes and capabilities. The largest are RFX-mod in Padova (Italy) and MST in Madison (USA). The experimental community includes also EXTRAP-T2R in Sweden, RELAX in Japan and KTX in China. Impressive improvements in the performance are the result of exploration of two lines: the high current operation (up to 2 MA) with the spontaneous occurrence of helical equilibria with good magnetic flux surfaces and the active control of the current profile. A crucial ingredient for the advancements obtained in the experiments has been the development of state-of-art active feedback control systems allowing the control of MHD instabilities in presence of a thin shell. The balance between achievements and still open issues leads us to the conclusion that the RFP can be a valuable and diverse contributor in the quest for fusion electricity.

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Section: Other Routes To Improved Confinementmentioning

confidence: 83%

Section: Multiple Helicity Regimementioning

confidence: 99%

Section: Other Routes To Improved Confinementmentioning

confidence: 99%

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The reversed field pinch

et al. 2021

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“…In reversed-field pinches (RFPs), which are inherently high-b devices, current-carrying filaments generated by the turbulence have been observed and studied by their magnetic signatures. 193,241,298 In tokamaks, evidence for fieldline bending and current transport by filaments comes almost exclusively from ELM observations. ELM filaments are commonly observed in tokamak H-modes 19,24,[32][33][34][35][36] (also see the review in Ref.…”

Section: Electromagnetic Effects On Blob-filaments and Elmsmentioning

confidence: 99%

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

2011

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A blob-filament (or simply “blob”) is a magnetic-field-aligned plasma structure which is considerably denser than the surrounding background plasma and highly localized in the directions perpendicular to the equilibrium magnetic field B. In experiments and simulations, these intermittent filaments are often formed near the boundary between open and closed field lines, and seem to arise in theory from the saturation process for the dominant edge instabilities and turbulence. Blobs become charge-polarized under the action of an external force which causes unequal drifts on ions and electrons; the resulting polarization-induced E × B drift moves the blobs radially outwards across the scrape-off-layer (SOL). Since confined plasmas generally are subject to radial or outwards expansion forces (e.g., curvature and ∇B forces in toroidal plasmas), blob transport is a general phenomenon occurring in nearly all plasmas. This paper reviews the relationship between the experimental and theoretical results on blob formation, dynamics and transport and assesses the degree to which blob theory and simulations can be compared and validated against experiments.

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“…These cameras have a particularly high sampling rate. Although the SXR signal is a lineintegrated measurement, it is considered that the emissivity is strongest at the flux surface tangent to the measurement chord [23]. The error in the radial localization depends on the line of sight and can be estimated from the camera geometry, the angle and the position of the resonant surface.…”

Section: Coherence Analysismentioning

confidence: 99%

Characterization of Alfvén eigenmodes using NBI during current ramp-up in the ASDEX Upgrade tokamak

Graca¹,

Lauber

Curran

et al. 2012

Plasma Phys. Control. Fusion

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Alfvén cascades (ACs) and beta-induced Alfvén eigenmodes (BAEs) have been studied in the ASDEX Upgrade tokamak during the current ramp-up phase of neutral beam heated (NBI) discharges using principally reflectometry, but also soft x-ray (SXR) and electron cyclotron emission imaging (ECEI). ACs have been observed on the tokamak high-field side and low-field side in reflectometer signals even in the absence of a cutoff. Under this condition it is shown that the response is not due to an interferometry effect but due to backscatter. The radial structure of BAEs and ACs has been obtained by cross-correlating the reflectometer with SXR, ECEI and magnetic signals. The reflectometer signals reveal a variety of Alfvén eigenmodes with different characteristics depending on the plasma heating scheme. Here, discharges with similar plasma parameters but varying NBI sources and/or additional electron cyclotron resonance heating were performed. It is shown that the bursting behaviour of ACs for q min < 2 depends on the NBI beam geometry. Also, a discrepancy in the n = 2 AC minimum frequency of a Grand Cascade is explained by the linear gyro-kinetic code LIGKA simulations which include energetic particle effects.

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Filamentary current structures in the Madison Symmetric Torus

Cited by 8 publications

References 28 publications

The reversed field pinch

The reversed field pinch

Convective transport by intermittent blob-filaments: Comparison of theory and experiment

Characterization of Alfvén eigenmodes using NBI during current ramp-up in the ASDEX Upgrade tokamak

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