Modelling nonlocal kinetic transport in 2D fluid SOL simulations

Accurate predictions of tokamak edge plasmas, as well as neutral dynamics and fuelling efficiency, relies on an accurate prediction of the plasma energy transport. Fluid plasma codes, that miss key kinetic effects in energy transport, may lead to significant error when used for predictions of future reactor devices. In low-collisionality conditions, supra-thermal electrons with very long mean-free-paths carry most of the parallel plasma energy, and energy transport becomes “nonlocal”. High energy gain fusion devices will exhibit for the first time both high opaqueness to neutrals and a very low collisionality SOL. It is presently envisioned that in either conventional or spherical tokamak pilot plants, main chamber SOL plasma temperatures will be high enough to invalidate the fluid approach, with kinetic effects becoming increasingly important to parallel heat transport. Full kinetic simulations are computationally expensive. ‘Reduced-kinetic’ models offer an alternative method for calculating the parallel heat flux component within fluid codes, with greater accuracy towards the “true” kinetic result at reduced computational cost. Employing such models in 2D edge plasma codes offers the potential to improve the accuracy of our predictions for future fusion reactors, and therefore increase their chances of success.