|Single cell electro-polishing at CEA Saclay : first results.|
|F. Eozénou, M. Bruchon, Y. Gasser, Y. Boudigou, B. Visentin, J.P. Charrier, S. Berry, C. Antoine, D. Reschke|
The goal of the Work Package 5.1 of the CARE SRF program is to study electro-polishing (EP) of niobium and thus isolate an ideal set of parameters for 1.3 GHz single cell cavity treatment that should be applied to industry. The more challenging aspect concerns acid composition's optimisation, made of a mixture of hydrofluoric (HF) and sulfuric (H2SO4) acids with possible additional water. Preliminary experiments have been carried out on samples to guide the program on single-cell cavities. In that way, a set-up for horizontal EP has been installed in our laboratory. This set-up has been successfully qualified with the standard recipe used at DESY since the first EP on TESLA-shaped cavity has reached an excellent gradient above 42 MV/m. The search for new parameters makes then sense. Different configurations have been investigated: higher temperature, lower voltage and new acids' concentrations. Dummy cavities have been electro-polished with a new mixture: 1vol HF(40w%) 2vol H2SO4(95w%) 7vol H2O, (1-2-7) with high water content. Different cavities have also been electro-polished and results including surface aspect, RF measurements and impurities forming will be related.