Feasibility of generating helical divertors for quasisymmetric or quasi-isodynamic geometries

Establish whether a helical divertor with toroidally continuous sharp edges, as targeted by optimizing modular coils for rotating lemon surfaces, can be generated for quasisymmetric or quasi-isodynamic plasma geometries.

Background

The work demonstrates an LHD-like helical divertor using modular coils and sharp-edged target surfaces, achieving reduced separatrix chaos. However, the target plasma surface was not optimized for core physics properties such as quasisymmetry (QS) or quasi-isodynamicity (QI).

Modern QS and QI configurations typically feature high-curvature ridges that are not toroidally continuous, raising uncertainty about compatibility with a helical divertor topology requiring a continuous sharp edge. The authors explicitly note that it remains to be seen whether such a divertor can be generated for QS or QI geometries.