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TY - CPAPER AU - Wenskat, M. AU - Steder, L. TI - Characterization of Optical Surface Properties of 1.3 GHz SRF Cavities for the European XFEL J2 - Proc. of International Conference on RF Superconductivity (SRF2015), Whistler, BC, Canada, Sept. 13-18, 2015 AB - The optical inspection of the inner surface of superconducting rf cavities is a well-established tool at many laboratories. Its purpose is to recognise and understand field limitations and to allow optical quality assurance during cavity production. Within the ILC-HiGrade programme at DESY, as part of the XFEL cavity production, an automated image processing and analysis algorithm has been developed that recognises structural boundaries. The count of features, the length of boundaries and their orientation can be used for characterisation. Appreciable differences are observed depending on the fabrication process at the vendor and the chemical treatment applied. The potential of this framework for automated quality assurance as an integral part of large-scale cavity production will be outlined. In addition, correlations between geometrical surface properties and the maximal accelerating field of twenty cavities have been found. These observations coincide with quench localisation by second sound of two cavities. The distribution of the limiting cell is vendor dependent, indicating weaknesses in the fabrication procedure. PB - JACoW CY - Geneva, Switzerland SP - 795 EP - 798 KW - cavity KW - background KW - electron KW - niobium KW - SRF DA - 2015/12 PY - 2015 SN - 978-3-95450-178-6 DO - 10.18429/JACoW-SRF2015-TUPB085 UR - http://srf2015.vrws.de/papers/tupb085.pdf ER -