Speaker
Description
We report on progress in modeling of plasma drifts and 3D turbulence using Hermes-3, in tokamak and stellarator configurations. During the past year improvements have been made to models for the diamagnetic and polarization currents, ion viscosity and energy conservation. Tokamak applications include simulation of turbulence in NSTX and NSTX-U configurations, with comparison to experimental data.
Stellarator boundary modeling is challenging due to the complex magnetic field topology and wall geometry, in addition to the many interactions between plasma, neutrals and surfaces present in modeling of tokamak divertors. The Flux-Coordinate Independent (FCI) method has emerged as a promising approach to plasma discretization [1,2] that has sufficient flexibility to model real 3D devices. Recent advances in BOUT++ include relaxation methods to find steady-state plasma potentials[3], support-operator method (SOM) based FCI operators that conserve fluxes to machine precision on complex meshes, and nonlinear solvers and preconditioners to accelerate the solution of steady-state transport calculations.
Progress has been made to port BOUT++ and Hermes-3 to GPUs. Field operators have been rewritten to use template expressions to enable kernel fusion. The design and tradeoffs and future plans will be discussed.