Advanced Global Thermal Model of Wendelstein 7-X Plasma Vessel

The experimental campaigns of the Wendelstein 7-X (W7-X) stellarator have now started on the way to phases with higher energy and longer plasma pulses (maximum 18 GJ per pulse and maximum pulse duration of 30 min). The operation campaign in 2022/2023 showed that the upgraded plasma-facing components (PFC) withstand
$>$
1 GJ pulses. Actively cooled components such as the high heat flux island divertors and pumping gap panels were successfully used for the first time, and other PFC such as wall panels, heat shields, and baffle modules were equipped with a water supply network prior to the campaign. This update combined with higher plasma loads leads to a redistribution and increase of the thermal loads on the complex 3-D-shaped plasma vessel (PV) wall, which is an important vacuum and thermal barrier between the plasma and the superconducting magnet system in the cryostat interspace. In particular, varying distances from the plasma lead to locally varying loads on the PFCs and diffused knock-on loads on the PV wall. The complexity of the updated PFC is not reflected in previous thermal calculations of the PV wall. The focus of the activity was the creation of a flexible global finite element (FE) model to analyze the complex interaction between the PFC and the PV wall by integrating simplified PFC structures, improved as-built models of the PV cooling system, and 254 ports. This new advanced global thermal model allows for indicating possible hotspots on the PV wall for further local analyses and to estimate potential deformations of the whole PV in thermo-mechanical analysis.