Pedestal Physics Enabling High Fusion Performance and Low Recirculating Power for EXCITE and Pilot Plant Designs

The pressure and temperature at the top of the pedestal play a key role in fusion performance, and complex physics within the narrow edge transport barrier regulates these. We employ and further develop the EPED model to predict the pedestal structure, and derive a set of metrics to evaluate pedestal contributions to performance. We review comparisons of EPED predictions to observations on several tokamaks, focusing on high pedestal regimes. Strong shaping and moderate aspect ratio facilitate operation with a high pressure pedestal limited by current-driven kink/peeling modes ("peeling limited") even at relatively high density. In the peeling-limited regime, the pedestal is predicted not to be degraded by high separatrix density, facilitating compatibility with a dense radiative divertor plasma. Optimization of the pedestal facilitates not only high fusion power density but also very high (>80%) bootstrap current fraction, enabling compact devices with low recirculating power and continuous operation. A regime is identified with intermediate R/a~2.3-2.7, and strong shaping, which holds promise for next-generation fusion devices such as a compact fusion pilot plant (CFPP) and an Exhaust and Confinement Integration Tokamak Experiment (EXCITE).