The performance of SRF cavities made of bulk Nb at high RF fields (peak surface magnetic field greater than about 90 mT) is characterized by exponentially increasing RF losses (high-field Q-slope or Q-drop), in the absence of field emission, which are often mitigated by a low temperature (100-140°C, 12-48h) baking. In this presentation, experimental results and phenomenological models to explain this effect will be reviewed. Recent theoretical calculations and experimental results suggest the possibility of anomalous RF losses being caused by magnetic vortices, either trapped or moving through the Nb surface.  New experiments to further prove this hypothesis and to possibly improve the overall cavity performance will be briefly discussed.

Thursday, October 1, 2009

3:30 p.m. - 4:30 p.m.
CEBAF Center, Auditorium

Talk Slides: (Slides)


Dr. Alex Bogacz or Anne-Marie Valente.