Zero-turbulence manifold in a toroidal plasma.

Journal article

Sheared toroidal flows can cause bifurcations to zero-turbulent-transport states in tokamak plasmas. The maximum temperature gradients that can be reached are limited by subcritical turbulence driven by the parallel velocity gradient. Here it is shown that q/ϵ (magnetic field pitch/inverse aspect ratio) is a critical control parameter for sheared tokamak turbulence. By reducing q/ϵ, far higher temperature gradients can be achieved without triggering turbulence, in some instances comparable to those found experimentally in transport barriers. The zero-turbulence manifold is mapped out, in the zero-magnetic-shear limit, over the parameter space (γ(E), q/ϵ, R/L(T)), where γ(E) is the perpendicular flow shear and R/L(T) is the normalized inverse temperature gradient scale. The extent to which it can be constructed from linear theory is discussed.

Authors: Highcock, E; Schekochihin, A; Cowley, S; Barnes, M; Parra, F

• Publication status: Published
• Journal: Physical Review Letters
• Volume: 109
• Issue: 26
• Pages: 265001
• Publication date: 2012-12-01
• DOI: 10.1103/physrevlett.109.265001
• EISSN: 1079-7114
• ISSN: 0031-9007
• Language: English
• Keywords: physics.plasm-ph