Effects of auxiliary heating on dc electric fields in the TEXTOR boundary

Moyer, R. A.; Nieuwenhove, R. Van; Oost, G. Van; Bora, D.; Conn, R.W.; Conrads, H.; Ivanov, R.S.; Laux, M.; Rusbüldt, D.; Schorn, R. P.; Telesca, G.; Vandenplas, P. E.

doi:10.1016/0022-3115(90)90062-r

Cited by 17 publications

(11 citation statements)

References 14 publications

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“…It is also observed in many diverted discharges that the measured fluctuation-induced flux is much too high to be consistent with global particle balance (DIII-D tokamak 23 , JET 36,22,26 ). Taken together, the above observations have led to the speculation that (3) there exists some inward particle transport mechanism that does not involve fine scale plasma turbulence such as large stationary convection cells, as suggested in some experiments [37][38][39][40] , and/or (4) there are large corrections that should be made to the fluctuation-induced flux estimate due to finite electron temperature fluctuations that are not being measured in many of these experiments, and/or (5) there exists a large poloidal asymmetry in the turbulent transport (ballooning hypothesis). However, with respect to speculation (4): Recent measurements in the Texas Experimental Tokamak-Upgrade (TEXT-U) 41 and in DIII-D 30 indicate that density and electron temperature fluctuations in the edge plasma tend to be in phase.…”

Section: Introductionmentioning

confidence: 87%

An interpretation of fluctuation induced transport derived from electrostatic probe measurements

LaBombard

2002

Physics of Plasmas

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Fluctuation-induced particle fluxes (Γ˜ñ φ) in the edge of Alcator C-Mod [Phys. Plasmas 1, 1511 (1994)] are inferred from a fast-scanning probe using standard analysis techniques. The magnitude and profile shape of Γ˜ñ φ is clearly inconsistent with fluxes inferred from global particle and power balance. These differences are difficult to reconcile if Γ˜ñ φ is interpreted as a measure of the particle flux in the unperturbed plasma. However, if Γ˜ñ φ is reinterpreted as the particle flux which must 'fill-in' the presheath zone formed by the probe, these inconsistencies are eliminated. In this case, an effective diffusivity in the presheath zone (D ps) can be estimated from Γ˜ñ φ. D ps is found to be in the range of diffusivities inferred from global particle balance (D SOL), indirectly supporting the hypothesis. However, the profile of D ps and its dependency on discharge conditions are markedly different than D SOL , implying that D ps is also not simply related to transport in the unperturbed plasma.

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Section: Introductionmentioning

confidence: 87%

An interpretation of fluctuation induced transport derived from electrostatic probe measurements

LaBombard

2002

Physics of Plasmas

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“…When adjacent field-lines charge to different voltages, there is a perpendicular electric field between them. This gives rise to E × B drifts and the important concept of rf-sheath-induced convection [28][29][30].…”

Section: Antenna (Near-field) Sheaths and Interaction With Edge Plasmamentioning

confidence: 99%

“…This gives rise to E×B drifts and the important concept of rfsheath-induced convection. [20][21][22] The effects of rf-induced convection have been seen indirectly in experiments. On JET, reduced particle confinement and increased SOL density scale length during monopole H-modes were attributed to rf-induced convection.…”

Section: Fw Launch Antenna-edge Interactions: Rf Sheathsmentioning

confidence: 99%

Nonlinear ICRF-plasma interactions

et al. 2006

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Abstract. The well developed linear theory of ICRF (including FW, HHFW and IBW) interactions with plasma has enjoyed considerable success in describing antenna coupling and wave propagation, and provides a well-known framework for calculating power absorption, current drive, etc. In some situations, less well studied nonlinear effects are of interest, such as flow drive, ponderomotive forces, rf sheaths, parametric decay and related interactions with the edge plasma. Standard ICRF codes have begun to integrate this physics to achieve improved modeling capabilities. This paper concentrates on basic rf-plasma-interaction physics with illustrative applications to tokamaks. For FW antennas, the parallel electric field near launching structures is known to drive rf-sheaths which can give rise to convective cells, interaction with plasma "blobs", impurity production, and edge power dissipation. In addition to sheaths, IBW waves in the edge plasma are subject to strong ponderomotive effects and parametric decay. In the core plasma, slow waves can sometimes induce nonlinear effects. Mechanisms by which these waves can influence the radial electric field and its shear are summarized, and related to the general (reactive-ponderomotive and dissipative) force on a plasma from rf waves. It is argued that there are significant opportunities now for new predictive capabilities by advances in integrated simulation.

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“…This potential is nearly constant along the equilibrium magnetic field but varies rapidly across it. The spatial variation of φ drives rapid E × B convection [12,20,23,24] which increases the flux of plasma to the antenna and thereby enhances the strength of the antenna-plasma interactions. The DC electric fields in the SOL and the convective fluxes have been measured with probes in several experiments (e.g.…”

Section: Introductionmentioning

confidence: 99%

Analysis of RF sheath interactions in TFTR

D’Ippolito¹,

Myra²,

Rogers³

et al. 1998

Nucl. Fusion

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New theoretical and experimental tools are applied to the analysis of ICRF antenna-edge plasma interactions in the Tokamak Fusion Test Reactor (TFTR) tokamak. A new numerical method for computing the three-dimensional rf sheath voltage distribution is used, and the quantitative predictions of rf sheath theory are compared with measurements of the edge density profile obtained by microwave reflectometry and with titanium impurity concentration data. It is shown that the local density depletion at the antenna is consistent with density pump-out by strong E × B convection into the Faraday screen. Modeling of the Faraday screen impurity influx shows that the calculated Ti impurity concentration based on this direct influx agrees with the measured concentration for π phasing. It is also shown that screening of impurity neutrals by ionization in the SOL is a large effect and increases with rf power. At high power over many shots, a fraction of the metal impurities migrates around the machine and is deposited on the limiters, providing a secondary source of titanium. The data shows that the central Ti concentration is strongly dependent on antenna phasing. Possible explanations for this phasing dependence are discussed.

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Effects of auxiliary heating on dc electric fields in the TEXTOR boundary

Cited by 17 publications

References 14 publications

An interpretation of fluctuation induced transport derived from electrostatic probe measurements

An interpretation of fluctuation induced transport derived from electrostatic probe measurements

Nonlinear ICRF-plasma interactions

Analysis of RF sheath interactions in TFTR

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