SOLPS-ITER simulations to study the impact of aspect ratio on edge fueling neutrals in tokamaks
In this paper,we examine the role of the aspect ratio on the neutral penetration and poloidal distribution for fixed magnetic geometry and plasma profiles using SOLPS-ITER. We start from an H-mode discharge from MAST [9], with its aspect ratio of 1.4 and shift the magnetic equilibrium and vessel in major radius to generate a new SOLPS-ITER simulation, doubling the aspect ratio to 2.8. The neutral density profile perpendicular to the magnetic flux surfaces is fitted by an exponential and we find that the opaqueness defined as the ratio between the electron pedestal density width and the neutral penetration depth is unaffected by changes in the aspect ratio.We do observe an increase in the neutral density close to the X-point on the high field side (HSF) as the aspect ratio increases. This substantial increase on the HFS is linked to an increase in the poloidal particle fluxes which shift down as a function of aspect ratio, leading to an increase in particle flux to the inner divertor and decrease to the outer divertor. The neutral density in the inner divertor is directly proportional to the increase in particle flux.