A Reduced Transport Model for Ion Heat Diffusivity by Gyro-Kinetic Analysis with Kinetic Electrons in Helical Plasmas

A high ion temperature plasma in the Large Helical Device is examined in the case in which the ion temperature gradient mode is unstable. The nonlinear gyro-kinetic simulation is performed to evaluate the turbulent ion heat diffusivity with the kinetic electron response. It is clarified that the decay time of zonal flows [S. Ferrando-Margalet et al., Phys. Plasmas 14, 122505 (2007)] decreases radially outward due to the trapped electron and the ion energy transport increases outward. To reduce the computational cost for applying to the dynamical transport simulation, an extended transport model for the ion heat diffusivity in terms of the mixing length estimate and the characteristic quantity for the linear response of zonal flows is proposed