Explorations of a non-resonant QA divertor for the Helios planar coil stellarator

The divertor of a fusion pilot plant (FPP) must survive extreme heat fluxes and enable efficient particle exhaust for the removal of impurities. Thea Energy, Inc. is designing a quasi-axisysmmetric (QA) stellarator FPP, "Helios", which will feature a resilient, non-resonant divertor solution. This is a strict requirement for the design of Helios as QA stellarators are not well-suited to island divertors (e.g. as implemented on W7-X) due to the shifting location of the island-forming edge resonance as plasma profiles vary. In this work, we show initial design efforts for a QA-compatible non-resonant divertor including field line tracing, target design, and first-wall heat flux estimations based on field-line diffusion (FLD) methods. We compare the behavior of the candidate divertor configuration with predictions and expectations from the literature and show the resilience of the solution to changes in plasma current and plasma pressure. Additional results are shown illustrating the sensitivity of the candidate magnetic geometry to perturbations in plasma profiles and/or magnetic geometry. Preliminary studies of baffling for neutral compression are also discussed.