Transition from multipactor discharge to ionization breakdown in microwave systems*

In microwave and RF systems, multipactor discharge and its transition to gaseous ionization breakdown remain one of the most significant limitations. Nonlinear effects can couple multiple carrier frequencies, cause instabilities and dispersion, and result in temporary failure as well as permanent damage. These phenomena occur for conducting and dielectric surfaces, in devices ranging from communications to high power microwave sources, to accelerators and even high gradient microwave circuits and devices. We examine the process of initial multipactor growth, surface heating and gas desorption, and subsequent evolution to ionization breakdown. We look at a variety of mitigation schemes, from spatio-temporal signal modulation to surface morphology and materials properties. We report on progress made in the recent decade on this important problem.