A Low-cost Gyrokinetic Code for Interpretive Transport Analysis of Tokamak Experiments

The X-point Gyrokinetic Code (XGC), primarily known for high-fidelity tokamak edge turbulence simulations, now enables low-cost axisymmetric gyrokinetic workflows to meet the demand for state-of-the-art transport analysis tools with fast time-to-solution. Axisymmetric XGC simulations – capable of full-f whole-volume simulation from the magnetic axis to the divertor plates – coupled to an advection-diffusion model, provide a practical, higher-fidelity alternative to widely-used fluid codes (e.g., SOLPS-ITER), capturing neoclassical physics accurately. These simulations are applicable to interpretive transport analyses of present-day experiments, ITER scenario development, and design optimization of fusion reactors such as Fusion Pilot Plants (FPPs). Essential kinetic effects – trapped particle dynamics, ExB and grad(B) drifts, bootstrap and Ohmic currents, Ware pinch, ion orbit loss, and parallel/perpendicular neoclassical transport – are captured without the approximations needed for fluid closures. We demonstrate and verify an interpretive transport analysis workflow that automatically optimizes anomalous transport coefficients in XGC using well-studied DIII-D discharges [Haskey et al., Phys. Plasmas 29, 012506 (2022)].