부산대학교 도서관

The quality factor of superconducting radio-frequency cavities made of high purity, bulk niobium increases with rf field in the medium field range (peak surface magnetic field between 20 and about 100 mT). The causes for this effect are not clear yet. The dependence of the surface resistance on the peak surface magnetic field is typically linear and quadratic. This contribution will present an analysis of the medium field Q-slope data measured on cavities treated with buffered chemical polishing (BCP) at Jefferson Lab, as function of different treatments such as post-purification and low-temperature baking. The data have been compared with a model involving a combination of heating and of hysteresis losses due to ''strong-links'' formed or weakened at niobium surfaces during oxidation, which correlate to {delta}{Delta}/kT{sub c} changes by baking.