Parametric design and engineering of non-resonant QA divertor structures for the Helios planar-coil stellarator

Thea Energy, Inc. is designing “Helios,” a planar-coil quasi-axisymmetric (QA) stellarator fusion pilot plant (FPP). Helios will feature a resilient non-resonant divertor solution, rather than an island divertor as is typical of other stellarators (e.g. W7-X). As an FPP, the divertor of Helios must survive extreme steady-state heat flux, efficiently exhaust impurities, exhibit resilience to neutron damage and hydrogen/helium embrittlement, minimize tritium retention, and be constructed out of low-activation materials. Because the plasma boundary of a stellarator is not axisymmetric, a QA non-resonant divertor will feature intricate non-axisymmetric geometry, which imposes unusual design challenges.

In this work, we show initial engineering efforts of QA non-resonant divertor structures, including parametric design of divertor targets and baffles to optimize magnetic shadowing, thermal and mechanical analyses of divertor structures, and design for manufacturing (DFM) considerations.