Regensburg 2022 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 25: Poster

KFM 25.10: Poster

Thursday, September 8, 2022, 15:00–18:00, P2

Dielectric loss measurements of CVD diamond disks for ITER windows — •Sabine Schreck¹, Gaetano Aiello¹, Pablo Estebanez², Andreas Meier¹, Dirk Strauss¹, and Theo Scherer¹ — ¹Karlsruhe Institute of Technology, Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany — ²F4E, Josep Pla 2, Torres Diagonal Litoral B3, 08019 Barcelona, Spain

Diamond disks manufactured by chemical vapor deposition (CVD) are essential elements of windows of the Electron Cyclotron Heating and Current Drive systems of fusion reactors like ITER. Diamond is selected as window material because of its high mechanical stability, high thermal conductivity and low dielectric loss. Only diamond disks with a low loss tangent guarantee a high transmission, i.e. a low absorption of microwave power in the disk. The latter results in moderate window temperatures and therefore in low thermal stresses. Hence, the measurement of the loss tangent is essential for the qualification of diamond disks for high-power windows. Dedicated measurement facilities (Fabry-Perot resonators) at KIT allow a high resolution measurement of the loss tangent at the disk centre (spherical set-up) as well as a mapping over the disk area to estimate its homogeneity (hemispherical set-up). Within a contract between F4E and KIT more than 60 diamond disks (D=70mm, t=1.11mm) produced similarly by MPA-CVD need to be qualified for their application in the ITER EC-system. The development of a dedicated test plan as well as initial results for the first disks delivered to KIT will be presented.