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Description
Operating gradients more than twice as high as those in bulk Nb cavities as well as significantly higher Q-values can be achieved by using nm-thin SIS (superconducting-insulating-superconducting) multilayers on the inner surface of a cavity to delay the penetration of vortices. Based on this theory, the University of Hamburg focuses on Atomic Layer Deposition (ALD) for thin film deposition as the most promising technique to coat SIS multilayers. A versatile material study provides insight into the interplay between the insulator film and the superconductor film under the influence of post-deposition thermal annealing. The results encompass depth profiles of as-deposited and annealed multilayer samples deduced from cross-sectional energy-dispersive X-ray spectroscopy (EDX) illustrating high-temperature annealing-induced changes in thin films. Moreover, the energy gap as well as the Dynes parameter are determined by measuring the complex optical conductivity at THz frequencies. These studies aim to use the newly developed HADES system (Hamburg's Atomic Layer Deposition Instrument for Enhanced Superconductors) to coat single-cell niobium cavities. The system's current commissioning is being compared with previously conducted simulations of its operation.