Relation among ITG turbulence, zonal flows, and transport in helical plasmas

Relation among the ion temperature gradient (ITG) turbulence, zonal flows, and the transport in helical plasmas is investigated by nonlinear gyrokinetic simulations. Local gyrokinetic simulations for helical field configurations are carried out employing various parameters such as the density and temperature gradients and local shears. From the simulation results, we construct a simple model function to represent ion heat diffusivity in terms of the turbulent fluctuations and zonal flow amplitude in helical plasmas. (author)