Implementation of a free-boundary equilibrium solver for the cloverleaf configuration and its implications for X-point radiators

Power exhaust is one of the critical challenges in plasma physics for a fusion power plant. The X-point radiator (XPR) regime, influenced by the magnetic topology of the plasma, represents a promising route to address this problem. To explore more favorable geometries and field-line topologies, a new free-boundary static equilibrium solver has been developed, extending its capability to include high-order null configurations, such as the cloverleaf (CL) divertor. Consistent results were obtained through benchmarking against the Solov’ev analytical solution and the numerical result from the FreeGS code. The CL configuration is presented based on the DIII-D geometry. Owing to the presence of an extended weak poloidal magnetic field region, this configuration exhibits a long connection length and strong flux expansion. These features indicate that the CL divertor is a promising candidate for XPR scenarios in future fusion devices.