Mechanisms limiting high gradient rf cavities

The specific mechanisms responsible for breakdown of rf cavities have been widely debated. A large number of different processes are thought to be involved, including field emission, surface contamination, mechanical stresses, plasma effects, explosive electron emission, a variety of heating mechanisms, mechanical imperfections, surface structure and chemical composition. We are attempting to model the surface effects that limit the operation of high gradient rf cavities using the HEIGHTS package. Models of individual processes are being developed and compared, in an attempt to evaluate the relative importance of these effects, specifically for the case of low frequency (200 - 800 MHz.) copper cavities, but probably applicable to other materials and frequencies.