Microturbulence and flow shear in high-performance JET ITB plasma

The transport, flow shear, and linear growth rates of microturbulence are studied for a JET plasma with high central q in which an internal transport barrier (ITB) forms and grows to a large radius. The linear microturbulence growth rates of the fastest growing (most unstable) toroidal modes with high toroidal mode number are calculated using the GS2 and FULL gyrokinetic codes. These linear growth rates, γlin, are large, but the flow-shearing rates, γExB (dominated by the toroidal rotation contribution), are also comparably large when and where the ITB exists. (author)