Thermo-mechanical analysis of plasma facing components of diagnostics in the Wendelstein 7-X stellarator

For long-pulse plasma operation of the W7-X stellarator, one of the most serious challenges for the design of in-vessel diagnostic systems is the thermo-mechanical problem. Thermal load from convective losses and from plasma radiation can reach up to 500 kW/m2 at some locations close to plasma. The typical thermal load from plasma radiation alone ranges from 10 kW/m2 to 100 kW/m2 as derived from 3D Monte-Carlo simulations. Most plasma facing diagnostic components require active cooling for the long-pulse plasma operation. Especially the design of optical components must be optimized to minimize thermal deformations. Finite element analyses (FEA) are performed for better understanding of thermo-mechanical problems on plasma facing components of diagnostics, and to guide the design of the diagnostic system. As examples the paper presents the FEA results of the Corner-Cube Retro-Reflectors for the CO2-laser interferometer and the movable pop-up probe arrays in the divertor.