The fusion code XGC: Enabling Kinetic Study of Multiscale Edge Turbulent Transport in ITER

Magnetic fusion experiments are essential for next-generation burning plasma experiments such as the International Thermonuclear Experimental Reactor (ITER). * The success of ITER is critically 530dependent on sustained high-confinement (H-mode) operation, which requires an edge pedestal of sufficient height for good core plasma confinement without producing deleterious large-scale, edge-localized instabilities. The plasma edge presents a set of multiphysics, multiscale problems involving a separatrix and complex three-dimensional (3-D) magnetic geometry. Perhaps the greatest computational challenge is the lack of scale separation; for example, temporal scales for drift waves, Alfvn waves, and edge localized mode (ELM) instability dynamics have a strong overlap. Similar overlap occurs in the spatial scales for the ion poloidal gyro-radius, drift wave, and plasma pedestal width. Microturbulence and large-scale neoclassical dynamics self-organize together nonlinearly. The traditional approach of separating fusion problems into weakly interacting spatial or temporal domains clearly breaks down in the edge. A full kinetic model (total-f nonperturbative model) must be applied to understand and predict the edge physics, including nonequilibrium thermodynamic issues arising from the magnetic topology (e.g., the open field lines producing a spatially sensitive velocity hole), plasma wall interactions, neutral and atomic physics [1,2].