Role of zonal flow predator-prey oscillations in triggering the transition to H-mode confinement.

University of California-Los Angeles, Los Angeles, California 90095, USA.
Physical Review Letters (Impact Factor: 7.73). 04/2012; 108(15):155002. DOI: 10.1103/PhysRevLett.108.155002
Source: PubMed

ABSTRACT Direct evidence of zonal flow (ZF) predator-prey oscillations and the synergistic roles of ZF- and equilibrium E×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 E×B shear due to the increasing ion pressure gradient.