Using Pedestal Physics to Close the Integrated Tokamak Performance and Exhaust (ITEP) Gap

The edge transport barrier, or "pedestal," provides the interface between the hot core fusion plasma, and the much cooler boundary plasma which exhausts heat and particles from the system. To close the ITEP gap, an order of magnitude improvement in the product of core fusion performance (measured by the product of pressure and bootstrap fraction) and parallel heat exhaust capability (measured by PB/R) is required, relative to both existing devices and ITER. Here we employ an updated version of the EPED pedestal model, both independently and coupled to core transport (TGLF) and boundary physics (SOLPS) models, to develop and optimize regimes which potentially close the ITEP gap. Strong shaping, moderate aspect ratio (R/a~2.3-2.7), and high field (B>~6T) facilitate operation with a high pressure pedestal limited by current-driven kink/peeling modes ("peeling limited," including the "Super H-mode" regime) even at relatively high density. In this peeling-limited regime, the pedestal is predicted not to be degraded by high separatrix density and pressure, facilitating compatibility with a dense radiative divertor plasma. Promising regimes are identified both for a demonstration device and a compact fusion pilot plant.