Information about the SciDAC-4 Center for

High-Fidelity Boundary Simulation (HBPS)

Our goal is to develop advanced simulation software, utilizing extreme parallelism and based upon a first-principles kinetic approach, to address the challenges associated with understanding the edge region of magnetically confined plasmas. This work is relevant to existing magnetic fusion experiments and essential for next-generation burning plasma experiments such as ITER. The success of ITER is critically dependent upon 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 multi-physics, multi-scale problems involving a separatrix and complex 3D magnetic geometry. Perhaps the greatest computational challenge is the lack of scale separation – temporal scales for drift waves, Alfvén waves, and ELM dynamics, for example, have 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*non-perturbative model) must be applied to understand and predict the edge physics including non-equilibrium 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.