A. Mancini (I): Power exhaust capabilities of Alternative Divertor Configurations

• Alessandro Mancini (Max Planck Institute for Plasma Physics)

R. Babin (P): Enabling stellarator optimization beyond cylindrical coordinates

• Robert Babin (IPP-Garching)

Historically, stellarator optimization has relied on cylindrical coordi- nates, which are well-suited for toroidal geometries. However, this coordi- nate choice inherently limits the design space, as it struggles to accurately represent configurations with a highly inclined magnetic axis or straight segments, both features that are increasingly relevant in modern stel- larator designs. In particular, both features are important in the search for stellarators with reduced boundary shaping. Such configurations, like the figure-8 stellarator, instead rely on the ”writhe” of the magnetic axis to generate rotational transform. To overcome this limitation, a more general, curve-following coordinate system has been implemented in the ideal MHD equilibrium solver GVEC. Nevertheless, integration with the broader stellarator optimization ecosystem, particularly the widely used optimization framework SIMSOPT, has relied on cylindrical coordinates. In this talk, I present the successful integration of GVEC with SIM- SOPT, enabling full-fledged stellarator optimization in non-cylindrical, curve-following coordinates. As a first demonstration, a figure-8 stellara- tor was optimized for a vacuum magnetic well, demonstrating access to previously unexplored regions of the stellarator design space.

L. Nitzsche (I): Measurement of core neutral density at W7-X

• Lucas Nitzsche (IPP Bereich Greifswald)