Bridging the pedestal gap: intermediate-fidelity models for pedestal transport
David Hatch
University of Texas at Austin
The projected cost of a magnetic confinement fusion power plant is strongly dependent on the level of plasma confinement that it can achieve. Confinement in tokamaks is largely determined by the quality of the edge ‘transport barrier’, called the pedestal. This is typically quantified by the pressure at the inner boundary of the pedestal, which effectively acts as a boundary condition for the bulk of the plasma. Despite the well-known causal relation between pedestal pressure and confinement, predictive capability remains limited when projecting performance in future devices. The two main approaches span the extremes of the fidelity hierarchy—from semi-empirical MHD-based models to high fidelity full-f gyrokinetics—but they leave much to be desired in terms of rigorous validation, breadth of applicability, and/or simulation cost. Though the ‘extremes’ are covered, there exists a gap—a potential sweet spot—in the middle for models that capture more physics than the lower fidelity options and retain the efficiency lacking at higher fidelity. Moreover, fast surrogate models can be applied to powerful optimization, control, or UQ workflows. This presentation will describe these ‘intermediate’ fidelity transport models for pedestal transport, their development and validation within a Bayesian framework, and outlook on future directions, including promising multi-fidelity applications.