NB COATING OF COPPER CAVITIES BY UHV CATHODIC ARC

bstract Niobium thin film coated copper RF cavities are an interesting alternative to niobium bulk cavities mainly because copper is cheaper, has higher thermal conductivity and better mechanical workability and stability than niobium. Unfortunately the observed degradation of the sputter-coated cavities quality factor with increasing accelerating voltage prevents their use in future accelerators specified to work at field values higher than 15MV/m. To try and overcome this limitation we have developed an alternative coating technique based on a cathodic arc system working under UHV conditions. Main advantages of this technique compared to standard sputtering are the ionized state of the evaporated material, absence of gases to sustain the discharge, high energy of atoms reaching the substrate surface and possibility to have high deposition rates. Recent results on the characterization of niobium film samples produced by UHV cathodic arc are presented, showing that the technique can produce high quality films under different angle of deposition. The system to demonstrate the deposition of a single cell cavity have been comm