A new chemical polishing procedure for lead-plated copper superconducting accelerating resonators

A procedure has been developed for polishing the thin electroplated lead coating used in Pb-Cu superconducting resonators which is much more effective than those available previously. Conventional polishing procedures cannot be used because their rapid action is inappropriate to the thin (10μ) lead layer. A previous procedure, designed for very slow action, rounded sharp edges to a radius of curvature of approximately 1μ. The new procedure provides nearly complete leveling of crystals 10μ in size. Results of tests on a β = 0.10 split loop accelerating resonator designed for the SUNYLAC Heavy Ion Booster will be reported. This resonator shows considerable improvement in performance over the previously tested cavity. On this basis, accelerator operation at an average field of 3 MV/m now seems feasible.