Application of Highly-Pure Copper Lining to Normal-Conducting Rf Cavities for an Electron-Positron Super B Factory

We apply a new copper lining with a high purity and a high electric conductivity to normal-conducting RF cavities for an electron-positron super B factory, in which four-times more beam current is required to be stored than in the present KEK B factory (KEKB). The lining is produced first by electroplating in an acid copper sulfate bath without brightener nor other organic additives, where the current is periodically reversed (“PR process”). Then the copper surface is electropolished to make it smoother. There are two differences between our application and the previous one to the accelerator components for J-Parc. The first one is the lining thickness; our target of 120 µ m is much thinner. The second one is that we have no mechanical polishing on the electroplated surface before electropolishing. In this paper, results of the quantitative estimations of the quality factor on the electroplated pillbox test cavity are reported together with microscale investigations of the copper surfaces.