WCI Fusion Theory Center, National Fusion Research Institute, South Korea

                 
Title :  Physics issues in turbulent transport in fusion plasmas and recent progress of gyrofluid simulations in internal transport barrier dynamics

Abstract :

The ultimate goal of magnetic fusion programs is to realize economically viable fusion reactors. A major scientific challenge in the magnetic fusion program is understanding and elucidation of the underlying fundamental physical processes leading to turbulent transport in order to provide predictive capability of fusion plasmas. Due to the inherent complexity and difficulty of the subject, predictive capability is not yet available, and fusion scientists still rely on empirical scaling relation based on experimental databases for the prediction of plasma performance, which should be overcome or improved significantly to accelerate the progress toward the quantitative capability. Recent development of large scale numerical simulations and precise diagnostics combined with emerging new theoretical ideas shed light on the progress of fusion science. In the first part of this presentation, I will give a brief overview of physics issues related to the turbulent transport in fusion plasmas, focusing on the scientific activities that have been carried out in WCI fusion theory center. Then, I will present recent development of gyrofluid simulations on the dynamics of internal transport barriers (ITB) showing a strong coupling to self-generated toroidal flow and featuring unique properties of hysteresis (i.e. implying the first order phase transition). Discussions of the role of momentum transport and Reynolds stress in the dynamics of transport barriers are followed. Finally, I present statistical characteristics of heat transport in ITB showing variety of non-diffusive phenomena when turbulence is strongly suppressed, which is akin to self-organized-criticality (SOC).