Simulating the Impact of Baffling on Divertor Performance Using SOLPS-ITER

TL;DR

This study uses SOLPS-ITER simulations to analyze how strong divertor baffling affects plasma detachment, neutral compression, and radiation patterns in tokamak divertors, revealing significant impacts on plasma behavior and edge conditions.

Contribution

It provides the first detailed simulation-based analysis of baffling effects on divertor performance, highlighting potential advantages for core-edge integration in tokamaks.

Findings

Baffling improves access to detachment on outer targets.

Tight baffling increases neutral compression and pumping efficiency.

Open divertor radiation extends along the plasma edge, affecting temperature profiles.

Abstract

Strong divertor baffling is a feature expected to have a number of advantages for core-edge integration in tokamaks, yet one which requires much more detailed and extensive study. In this work, the impacts of baffling on a hydrogenic plasma are studied in isolation, through artificial fixed-fraction impurity SOLPS-ITER simulations. These simulations are of the connected double null Super-X divertor on the MAST-U tokamak, with extreme cases of a closed and open divertor. Simulations show a divertor with a tightly baffled entrance can lead to better access to detachment on the outer targets, likely caused by reduced convection upstream. Adding tight baffling at the throat also leads to two orders of magnitude increase in neutral compression, and an order of magnitude more efficient pumping, with more peaked core density profiles. Finally, in contrast to the localised radiation of the closed divertor, the open divertor shows radiation along the entire plasma edge which moves upstream and inward into the core as detachment evolves; leading to sub-10eV temperatures in the near SOL at x-point.