R&D at JLAB towards high performance superconducting RF cavities

Abstract:  Recent advances in the processing of bulk superconducting radio frequency (SRF) niobium cavities via interior surface impurity diffusion have resulted in significant improvements in their quality factor (Q0). The motivation for the development of these processes is to reduce the cryogenic operating cost of current and future accelerators while providing reliable operation. The potential for higher Q0 in SRF cavities was first realized by titanium doping during high temperature annealing of SRF cavity at 1400 [degrees Celsius] and later by nitrogen doping at 800 [degrees Celsius] followed by electropolishing (EP). However, despite the increase in Q0, the quench field of the cavities doped by titanium or nitrogen is often limited to much lower values than achieved by standard treatments. Progress has been made when the cavities are heat treated at lower temperature in order to preserve the accelerating gradient with high quality factors. In this talk, I will review the recent R&D at Jefferson Lab on SRF cavities and samples processed along the cavity in order to better understand the mechanism behind the high quality factor.