The Impact of Defects on Q0 for HIE-ISOLDE High-Beta Quarter-Wave Resonators

Superconducting quarter-wave resonators (QWRs) will be used in the SC linac for the HIE-ISOLDE project at CERN. The QWRs will be working at 4.5 K with an operating frequency of 101.28 MHz. The maximum dissipated power in the cavity is required to be 10 W at a gradient of 6 MV/m. The QWRs are niobium coated on copper substrates, thus the niobium film quality has a direct impact on the cavity performance. This note calculates the impact of defects on cavity Q0 at different locations on the cavity inner surface