Core transport predictions of SPARC tokamak plasmas with flux-matched nonlinear gyrokinetic simulations

Predicting core gradients in tokamak plasmas using first-principles based models has long been the goal of transport research, but it has largely been intractable due to the large computational expense of nonlinear turbulent simulations. Given this high computational cost, the tokamak transport community has relied on a set of tools that span from empirical methods to quasilinear models of turbulence to scope and study future devices, while only using full nonlinear gyrokinetic simulations as standalone, spot-check validation studies. This talk will present the PORTALS workflow that reduces the computational cost of first-principles, multi-channel, non-linear gyrokinetic profile predictions of the plasma core. Thanks to this, the core of SPARC—a burning-plasma device under construction by Commonwealth Fusion Systems— has been extensively studied and predicted with nonlinear CGYRO. This talk will introduce the need of flux-matched simulations to enable profile predictions, will present the fundamentals of the PORTALS technique and will discuss the findings simulating the core of SPARC, from the impact of edge pressure to impurity effects on turbulence stabilization.