Investigation on Barrel Polishing for Superconducting Niobium Cavities

Barrel polishing was applied to L-band niobium cavities instead of buffing. For the TRISTAN superconducting cavities, buffing had been used for every half cell as the pre-finishing of electropolishing. It demands specialists and a rather high cost. For the mass-production as a superconducting linear collider like TESLA, an easier and cheaper method has to be developed. Barrel polishing seems to satisfy these requirements. Using combination of this method and electropolishing, field gradient higher than 30 MV/m with Qo - 1010 has achieved by a comparatively small amount of removal thickness.