University Siegen, Siegen, Germany
As part of efforts to improve the performance of thin film coated accelerating cavities, improvement of the topography of the surface of copper is being pursued. This is known to strongly affect the properties of the deposited superconducting thin film. This study focuses on determining the optimal procedure to enhance homogeneity and smoothness of the copper surface. OFHC copper substrates have been processed using mechanical polishing (MP), chemical polishing (CP) and electropolishing (EP) procedures as well as a combina-tion thereof. The parameters of each of the procedures have been tested and optimised to produce the smoothest surface possible. The resulting samples have been analysed using a scanning electron microscope, a laser profilometer and a confocal microscope. Results indicate the superior per-formance of electrochemical polishing over chemical polishing in terms of planarization efficiency, while a combination of mechanical polishing followed by electropolishing provides the most homogeneous and smooth surface when utilising the critical current density of the electrolyte.
