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Role of Zonal Flow Predator-Prey Oscillations in Triggering the Transition to H-Mode Confinement

2012; American Physical Society; Volume: 108; Issue: 15 Linguagem: Inglês

10.1103/physrevlett.108.155002

1092-0145

L. Schmitz, L. Zeng, T. L. Rhodes, J.C. Hillesheim, E. J. Doyle, R. J. Groebner, W. A. Peebles, K.H. Burrell, G. Wang,

Laser-Plasma Interactions and Diagnostics

Direct evidence of zonal flow (ZF) predator-prey oscillations and the synergistic roles of ZF- and equilibrium $\mathbit{E}\ifmmode\times\else\texttimes\fi{}\mathbit{B}$ flow shear in triggering the low- to high-confinement (L- to H-mode) transition in the DIII-D tokamak is presented. Periodic turbulence suppression is first observed in a narrow layer at and just inside the separatrix when the shearing rate transiently exceeds the turbulence decorrelation rate. The final transition to H mode with sustained turbulence and transport reduction is controlled by equilibrium $\mathbit{E}\ifmmode\times\else\texttimes\fi{}\mathbit{B}$ shear due to the increasing ion pressure gradient.