Predictive multi-scale gyrokinetic transport simulation capability for stellarator FPPs using Trinity3D+GX+KNOSOS

Evaluation of a stellarator FPP design requires the capability to predict the equilibrium profiles (and hence fusion power) attainable by the device subject to transport. Trinity3D+GX+KNOSOS is a new framework that leverages multi-scale gyrokinetic theory to simulate macro-scale profile evolution in stellarators due to turbulent and neoclassical processes. To simulate turbulence we use GX, a GPU-native pseudo-spectral gyrokinetic code that targets fast reactor-relevant calculations. Neoclassical transport is computed by the KNOSOS code, which uses orbit-averaging to solve the drift kinetic equation very efficiently at low collisionality. Both GX and KNOSOS use a radially-local approach, enabling a series of GX and KNOSOS calculations to be embedded in parallel in the Trinity3D transport solver for tractable fusion profile prediction (and evolution) calculations. An implicit Newton method is used to time-evolve the transport equations on the timescale of the energy confinement time. Ion temperature profile predictions subject to ion temperature gradient turbulence can be completed in less than an hour, while multi-channel calculations including electron temperature and density profile predictions can be completed in roughly a day. We will demonstrate a validation of the framework via modeling of W7-X plasmas and discuss future plans for applying the framework to stellarator FPP design and optimization.