SOLPS-ITER Simulation of MAST Opaqueness versus Aspect Ratio

For continuous tokamak operation, with a high core density, constant fueling through recycling, gas puffing or pellets will be necessary. However, in future large-size devices and at higher density, opaqueness, defined as n_e x a, will increase, reducing the ability of neutrals to penetrate past the separatrix [1]. The opaqueness depends on n_e approximated as the average of pedestal and separatrix electron densities, and a which is the minor radius. It is unclear how changes in aspect ratio affect opaqueness. In this poster, we will study the relationship between neutral penetration and aspect ratio using SOLPS-ITER simulation. We will start with matching an H-mode from MAST to determine boundary conditions and radial transport coefficients. We will in SOLPS-ITER increase the major radius, while keeping all other aspects identical to increase the aspect ratio to match the one in DIII-D in multiple steps. We will study the changes in neutral density as a function of aspect ratio in these SOLPS-ITER simulations.

[1] S. Mordijck, Overview of density pedestal structure: Role fueling versus transport, Nucl. Fusion (2020) http://iopscience.iop.org/10.1088/1741-4326/ab8d04