A New Workflow for Simulating X-point target and Snowflake Divertors in SOLPS-ITER

Alternative divertor configurations such as snowflakes or X-point targets may be crucial for reducing steady-state heat loads for reactor tokamaks, providing strong motivation for their extensive study. However, to date, the snowflake and X-point target have not been simulated extensively in codes with kinetic treatment of neutrals such as SOLPS-ITER. This is primarily because the SOLPS-ITER grid builder CARRE cannot be applied to such divertors, and the physics modules of SOLPS-ITER are not expecting such geometries. Though code modifications have been made to allow for snowflake simulations previously (Pan O et al. Plasma Physics and Controlled Fusion. 2020.), the generalisation of these changes has been challenging.

In this work we have developed a new workflow to simulate snowflake and X-point target divertors in SOLPS-ITER. The workflow uses the external grid builder INGRID along with custom-built conversion routines to generate the required input files. The SOLPS-ITER source is also edited to identify a snowflake or X-point target geometry, without affecting present functionality in the code. Along with this novel workflow, the first SOLPS-ITER simulations of the X-point target will be presented. These simulations focused on a single null SPARC X-point target equilibrium and are compared to a similar single null standard SPARC geometry. Simple analysis using two-point model physics supports the validity of these novel simulations.