Engineering tool for the optimization of leading edges in a tungsten-based divertor in W7-X: How to optimize adjacent chamfers

Abstract

Leading edges on the divertor surface of fusion devices are typically mitigated through tilting or chamfering the target components, so as to keep the potential leading edge unexposed to the particle flux. However, for neighboring components subjected to impinging particles from opposite direction, chamfering one component can lead to an increased size of leading edge on the neighboring component. The Wendelstein 7-X (W7-X) fusion device is particularly sensitive to this issue, as it features a great variety of magnetic configurations, each with a unique particle deposition pattern. This study uses thermal finite element method (FEM) simulations to analyze the thermal performance and design parameters of symmetric and asymmetric chamfering in divertor targets. For symmetric load cases, the effect of chamfer length and depth on maximum temperature is investigated. Key chamfer design trends are established to optimize the temperature by making the chamfer deep enough to avoid a leading edge while making the chamfer long enough to keep the heat load on the chamfer under a limit threshold. Based on these findings, an iterative algorithm is presented for asymmetric chamfer configurations, ensuring feasible solutions under different thermal loads. This work introduces a novel geometric classification of asymmetric chamfering scenarios in stellarator divertors, and presents the first practical algorithm capable of identifying feasible chamfer geometries under asymmetric bi-directional loading—an issue not addressed in existing tokamak-focused literature. It forms a part of a more comprehensive divertor design and optimization tool for W7-X under development.