Observation of the L-H confinement bifurcation triggered by a turbulence-driven shear flow in a tokamak plasma.
Comprehensive 2D turbulence and eddy flow velocity measurements on DIII-D demonstrate a rapidly increasing turbulence-driven shear flow that develops ∼100  μs prior to the low-confinement (L mode) to high-confinement (H mode) transition and appears to trigger it. These changes are localized to a narrow layer 1-2 cm inside the magnetic boundary. Increasing heating power increases the Reynolds stress, the energy transfer from turbulence to the poloidal flow, and the edge flow shearing rate that then exceeds the decorrelation rate, suppressing turbulence and triggering the transition.
University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Yan
University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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McKee
University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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Fonck
General Atomics, PO Box 85608, San Diego, California 92186-9784, USA.
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Gohil
General Atomics, PO Box 85608, San Diego, California 92186-9784, USA.
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Groebner
General Atomics, PO Box 85608, San Diego, California 92186-9784, USA.
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Osborne