Enhancement of the Bootstrap Current in a Tokamak Pedestal

Kagan, Grigory; Catto, Peter J.

doi:10.1103/physrevlett.105.045002

Cited by 18 publications

(45 citation statements)

References 22 publications

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“…We then proceed by comparing the revised formula for the impurity flow with the boron flow measured in banana regime C-Mod pedestals to find that agreement between the theory and experiment is noticeably improved upon accounting for the electric field effect on the main ion orbits [5]. This comparison verifies the role of the electric field in modifying the main ion flow and supports our conclusion that the bootstrap current is enhanced in a banana regime pedestal [6].…”

Section: Introductionsupporting

confidence: 64%

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Neoclassical Theory of Pedestal Flows and Comparison with Alcator C‐Mod Measurements

Kagan

Marr

Pusztai

et al. 2012

Contrib. Plasma Phys.

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Neoclassical implications of the strong radial electric field, inherently present in an H-mode tokamak pedestal, are considered. The main ion poloidal flow in the pedestal is predicted to be reduced in magnitude, or even reversed, compared with its core counterpart. The resulting change in the neoclassical formula for the impurity flow is shown to result in improved agreement with boron measurements in the Alcator C-Mod pedestal. In addition, due to the ion flow being modified, the bootstrap current is expected to be enhanced in the pedestal over conventional predictions.

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Section: Introductionsupporting

confidence: 64%

“…(18) for the main ion flow in place of the usual formula. As a result, the pedestal bootstrap current is found to be [6] J bs = −1.46 √ cI B (Z 2 + 2.21Z + 0.75) Z(Z + 1.414) dp dψ − (2.07Z + 0.88)n e (Z 2 + 2.21Z + 0.75)…”

Section: Discussionmentioning

confidence: 99%

Neoclassical Theory of Pedestal Flows and Comparison with Alcator C‐Mod Measurements

Kagan

Marr

Pusztai

et al. 2012

Contrib. Plasma Phys.

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show abstract

“…An additional consequence of our verification of the electric field role in modifying the impurity flow is the associated enhancement of bootstrap current in the banana regime pedestal [18]. That is, the theoretical predictions for the pedestal modifications to both the impurity flow and bootstrap current originate from the same observation that the electric field effect on ion drift orbits leads to the poloidal flow of background ions being reduced in magnitude, or even reversed, compared to its core counterpart.…”

Section: Discussion and Summarymentioning

confidence: 63%

The effect of the radial electric field on neoclassical flows in a tokamak pedestal

Kagan

Marr

Catto

et al. 2011

Plasma Phys. Control. Fusion

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Conventional formulas for neoclassical flows become inapplicable in subsonic tokamak pedestals with poloidal ion gyroradius scales since the associated strong radial electric field modifies the background ion orbits. The discrepancy has been measured to be substantial in the banana regime on Alcator C-Mod. We demonstrate that new expressions for the poloidal ion flow in the pedestal, that include the effect of the background electric field, are consistent with the boron impurity flow measurements in Alcator C-Mod.

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“…In this paper we show the isomorphism does extend to neoclassic al transport and to the residual zonal flow even when these q uantities are modified by a radial electric field E ψ . These "finite-E ψ " modifications were calculated recently for tokamaks by Kagan et al in [10][11][12][13][14][15][16] is th e poloidal field. Secondly, the canonical angular m omentum * Ψ is used as the "radial" coordi nate in the kinetic equation, and the transit average is r edefined to be an integral along a constant-* Ψ path instead of along a flux surface.…”

Section: Introductionmentioning

confidence: 97%

Effects of the radial electric field in a quasisymmetric stellarator

Landreman

Catto

2010

Plasma Phys. Control. Fusion

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Recent c alculations have shown that a radial el ectric field can significantly alter the ion flow, neoclassical ion heat flux, bootstrap current, and residual zonal flow in a tokamak, even when the × E B drift is much sm aller th an the ion therm al speed. Here we show the novel analy tical methods used in these calculations can be adapte d to a quasisy mmetric stellarator. The methods are based on using the conserved helical momentum * ψ instead of the poloidal or toroidal flux as a coordinate in the kinetic equation. T he calcu lations also em ploy a m odel collision ope rator which keeps only the velocity-space derivatives normal to the trapped-passing boundar y, even as this boundar y is shifted and deform ed by the × E B drift. We prove the iso morphism between quasisymmetric stell arators and tokamaks extends to the finite-× E B generalizations of both neoclassical t heory and residual zonal flow. The electric field i n the HSX s tellarator may be sufficient for these finite-× E B effects to be significant.

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Enhancement of the Bootstrap Current in a Tokamak Pedestal

Cited by 18 publications

References 22 publications

Neoclassical Theory of Pedestal Flows and Comparison with Alcator C‐Mod Measurements

Neoclassical Theory of Pedestal Flows and Comparison with Alcator C‐Mod Measurements

The effect of the radial electric field on neoclassical flows in a tokamak pedestal

Effects of the radial electric field in a quasisymmetric stellarator

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