Generation of non-axisymmetric scrape-off layer perturbations for controlling tokamak edge plasma profiles and stability

A critical requirement for tokamak fusion reactors is the control of the divertor heat load, both the time-averaged value and the impulsive fluxes that accompany edge-localized modes. We propose driving toroidally varying currents through the scrape-off layer (SOL) plasma both to broaden the SOL by...

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Bibliographic Details
Published in:Physics of plasmas 2012-05, Vol.19 (5), p.056124-056124-9
Main Authors: Joseph, Ilon, Cohen, Ronald H., Rognlien, Thomas D., Ryutov, Dmitri D.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AMPLITUDES
ASYMMETRY
CONVECTION
DISTURBANCES
DIVERTORS
EDGE LOCALIZED MODES
ELECTRIC POTENTIAL
HEATING LOAD
ITER TOKAMAK
PLASMA RADIAL PROFILES
PLASMA SCRAPE-OFF LAYER
PRESSURE GRADIENTS
PUMPING
SHEAR
STABILITY
STEADY-STATE CONDITIONS
TURBULENCE
WAVELENGTHS
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Summary:A critical requirement for tokamak fusion reactors is the control of the divertor heat load, both the time-averaged value and the impulsive fluxes that accompany edge-localized modes. We propose driving toroidally varying currents through the scrape-off layer (SOL) plasma both to broaden the SOL by inducing radial convection and to control the edge pressure gradient by inducing resonant magnetic perturbations. The generation of additional convective transport via steady-state convective cells or increased turbulence drive requires that the electric potential perturbations exceed a threshold in amplitude that depends on wavelength. The generation of a coherent magnetic perturbation is optimized by choosing the appropriate width and phasing of the biasing region at the target plate in order to optimize the profile of the SOL current. Longer wavelength modes produce a larger effect because they are not sheared as strongly by the magnetic X-point. Generation of the necessary currents is challenging due to the possibly substantial power requirements and the possible need for internal insulators. We analyze passive current-drive mechanisms that rely on puffing and pumping of neutral gas in a toroidally asymmetric fashion using the UEDGE code to model the ITER divertor.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.3702048