Comparing neutral density profiles between a spherical and regular aspect ratio tokamak

In current-day magnetic confinement devices, the ionization of neutrals inside the separatrix contribute to the steep electron density profiles. However, in reactor regimes, neutrals will be ionized in the SOL, directly impacting the shape of the electron density profile [1]. The ionization of neutrals does not only have an impact on the electron density but can also act as an energy and momentum sink and directly affect the radiation by impurities. We use SOLPS-ITER to model a MAST H-mode discharge. We will extract the transport coefficients by matching the experimental midplane profiles. By having SOLPS match the experimental profiles, we will be able to self-consistently extract the neutral density profiles. The compactness of spherical tokamaks suggests that neutrals will penetrate deeper than in regular devices. Therefore, we will compare the neutral density profile characteristics in a spherical tokamak environment to those of a regular aspect ratio tokamak.

 

[1] Mordijck, S., 2020. Overview of density pedestal structure: role of fueling versus transport. Nuclear Fusion, 60(8), p.082006.

 

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences DE-SC0021306, DE-SC0019302, DE-SC0007880.