Core Performance Predictions with Nonlinear Gyrokinetics and Implications to Scope Burning-Plasma Tokamaks

Surrogate-based techniques as implemented in the PORTALS framework [P. Rodriguez-Fernandez Nucl. Fusion 2023] are used to predict core kinetic profiles and fusion performance in tokamaks directly with nonlinear gyrokinetic simulations. The unprecedented fidelity of the profile predictions (enabled by the use of nonlinear CGYRO for turbulent transport) at a moderate computational cost opens up new pathways for the study of core transport. Predictions of performance in upcoming burning plasmas in SPARC and ITER are used to build confidence in their design and to plan and optimize experimental campaigns. Multi-channel predictions of core kinetic profiles with self-consistent energy exchange are utilized to validate ion scale gyrokinetics in the study of isotope effect in JET Ohmic plasmas. It is found that ion-scale nonlinear CGYRO underpredicts ion transport as the ion mass decreases from tritium to deuterium to hydrogen, which points to the potentially important role of high wavenumber or cross-scale effects in the explanation of isotope effect in JET Ohmic plasmas.