A general model of high gradient limits

Recent experimental work done to develop high gradient, low frequency cavities for muon cooling has led to a model of rf breakdown and high gradient limits in warm structures. We have recently been extending this model to try to explain some superconducting rf quench mechanisms, as well as DC and dielectric breakdown. The model assumes that the dominant mechanisms in warm metal systems are fractures caused by the electric tensile stress, and surface micro-topography that is strongly determined by the cavity design and history. We describe how these processes can determine all measurable parameters in warm systems. With superconducting systems, these mechanisms also apply, however field emission, impurities and temperature produce a somewhat different picture of quenching and pulsed power processing. We describe the model and some recent extensions and improvements.