Regensburg 2025 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 15: Crystal Structure Defects / Real Structure / Microstructure

KFM 15.3: Vortrag

Donnerstag, 20. März 2025, 10:15–10:30, H9

Single- and polycrystalline diamond characterization with superconducting microresonators — •Francesco Mazzocchi¹, Martin Neidig², Sebastian Kempf², Dirk Strauß¹, and Theo Scherer¹ — ¹Karlsruhe Institute Of Technology IAM-AWP — ²Karlsruhe Institute Of Technology IMS

The development of high optical quality, ultra-low-loss single-crystal diamond windows is essential for the realization of future nuclear fusion facilities, such as DEMO, due to the anticipated increase in power for microwave ECRH systems. So far, accurate measurement of the dielectric properties (εr and tanδ) of these materials has primarily relied on Fabry-Perot microwave resonators in different setups, with a resolution limit around 1E-5 in the determination of the loss tangent. Superconducting thin-film resonators, capable of reach Q factors in excess of 1E6, have the potential to assess the dielectric characteristics of ultra-low-loss materials like single- and polycrystalline diamond while offering a significant boost in resolution when compared to the state-of-the-art Fabry-Perot resonance cavities. We hereby report measurements performed at low (4 - 9 K) an ultra-low (10 - 700 mK) temperatures of several samples including single and poly-crystalline diamond. The samples have been grown with different techniques, including CVD, cloning and HPHT processes.

Keywords: polycrystalline; CVD; resonators; superconductor; diamond