Description
In recent years, the stellarator concept has attained increasing attention as an alternative path to a fusion reactor. The Wendelstein 7-X (W7-X) experiment has successfully demonstrated power and particle exhaust with the island divertor, achieving high-performance operation and homogeneous detachment. However, the current open divertor geometry suffers from an unfavorable scalings of divertor density and neutral pressure with upstream density, posing challenges for power and particle exhaust towards a reactor. Despite these limitations, W7-X has significant flexibility in operational and magnetic configuration parameters, allowing for a better understanding of the complex 3D geometry and relevant physics, both in full and simplified models. Recent advancements in imaging diagnostics have provided clear signatures of the 3D structure of the island divertor plasma, and emerging reactor-relevant scaling approaches are being developed. Advances in modeling capabilities enable mean-field and turbulence simulations with the drift-reduced Braginskii model, which are paired with W7-X observations to gain insight into island divertor physics. The boundary island geometry is becoming part of magnetic configuration optimization for future reactor designs, and refined insights into geometric island parameters are being developed to tailor properties for new concepts. Initial results suggest promising paths towards reactor-relevant exhaust performance.