A comparison of Gkeyll and SOLPS-ITER radiation for long leg fusion pilot plant

Gyrokinetic simulations using the edge code Gkeyll are performed for a fusion pilot plant SOL with a long leg. Various impurities of interest for a radiating divertor (Li, N, Al, Ar) are included. These simulations are then compared to simulations using the fluid SOLPS-ITER code.

The effect of the impurity mass on the impurity's heating is examined to study the difference in impurity entrainment from the potential. This can be a substantial effect especially when the impurity ion temperature is low. Lower impurity temperatures are more likely in the long mean free path regimes expected in the SOL of burning plasmas as they have have less collisional heating. We find that since the heating scales as the impurity mass and low temperature ions do not have the energy necessary to overcome the potential, the heavier impurities are confined to the divertor better. Further, since SOLPS-ITER uses only a single ion temperature, SOLPS-ITER simulations of the same impurity transport do not observe this improved confinement. Additionally, using the kinetic formulation of line radiation in Gkeyll (applicable to continuum kinetic codes), we analyze non-Maxwellian effects on the radiation and how this kinetic radiation varies with element and charge state.