Particle transport studies with applied resonant fields on TEXT

McCool, S. C.; Wootton, A. J.; Kotschenreuther, M.; Audemir, A.Y.; Bravenec, R. V.; deGrassie, J.S.; Evans, T.E.; Hickok, R. L.; Richards, B.; Rowan, W. L.; Schoch, P. M.

doi:10.1088/0029-5515/30/1/014

Cited by 70 publications

(70 citation statements)

References 16 publications

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“…Results with Orbit are consistent with maps of connection length made with field line tracing using the vacuum field approximation and a axisymmetric plasma equilibrium [35]. Previous results have pointed to the formation of island convective cells due to E × B flows around magnetic islands [43,44,45,46].…”

Section: Methodssupporting

confidence: 81%

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

et al. 2015

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The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted with simulations with the Hamiltonian guiding center code Orbit. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for theseeffects. An analytical model for the plasma potential is implemented in the code Orbit, and analyses of ion and electron radial diffusion show that both ion-and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggests that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

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Section: Methodssupporting

confidence: 81%

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

et al. 2015

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“…These short connection length flux tubes should also transport efficiently the electric potential from the walls deep into the plasma, namely, to the deepest perturbed island chains. This statement is in agreement with a previous observations on TEXT [19] where the potential was measured by a heavy ion probe; the electric field penetrates roughly to the q 2 surface and influences the diffusion coefficient. Probe measurements on CSTN-II [20] show as well the modification of the electric field in the ergodic region.…”

supporting

confidence: 93%

Improved Confinement due to Open Ergodic Field Lines Imposed by the Dynamic Ergodic Divertor in TEXTOR

et al. 2007

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The ergodization of the magnetic field lines imposed by the dynamic ergodic diverter (DED) in TEXTOR can lead both to confinement improvement and to confinement deterioration. The cases of substantial improvement are in resonant ways related to particular conditions in which magnetic flux tubes starting at the X points of induced islands are connected with the wall. This opening process is connected with a characteristic modification of the heat deposition pattern at the divertor target plate and leads to a substantial increase and steepening of the core plasma density and pressure. The improvement is tentatively attributed to a modification of the electric potential in the plasma carried by the open field lines. The confinement improvement bases on a spontaneous density built up due to the application of the DED and is primarily a particle confinement improvement.

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“…It has been shown in other tokamak devices that an enhancement in core plasma particle transport occurs with the application of a stochastic boundary [4,5]. Here, we report on a systematic study of the n e pump-out associated with the turnon of the RMP over a wide range of operating conditions, including shapes and collisionalities similar to those anticipated in ITER.…”

Section: Introductionmentioning

confidence: 83%

Experimental comparison of recycling and pumping changes during resonant magnetic perturbation experiments at low and high collisionality in DIII-D

Unterberg

Brooks

Evans

et al. 2009

Journal of Nuclear Materials

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Particle transport studies with applied resonant fields on TEXT

Cited by 70 publications

References 16 publications

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

Improved Confinement due to Open Ergodic Field Lines Imposed by the Dynamic Ergodic Divertor in TEXTOR

Experimental comparison of recycling and pumping changes during resonant magnetic perturbation experiments at low and high collisionality in DIII-D

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