Turbulence regulation and transport barriers in laboratory plasmas

We discuss the effect of shearing on transport and the formation of transport barriers. The focus is primarily on laboratory plasmas where the formation of transport barrier (the L-H transition or the formation of internal transport barrier) is thought to originate from turbulence regulation by shearing by (coherent) mean E × B flows and (random) zonal flows. We provide quantitative discussion on the reduction of turbulent transport by these flows and elucidate their roles in the barrier formation.