Résumé du preprint DAPNIA-07-187

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.


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