Ping-Pong Modes: A New Form of Multipactor

The multipactor is a vacuum discharge based on a secondary electron emission. A novel resonant form is proposed that combines one- and two-surface impacts within a single period, provided the total transit time is an odd number of rf half-periods and the product of secondary yields exceeds unity. For low fD products, the simplest such mode is shown to significantly increase the upper electric field boundary of the multipacting region and lead to overlap of higher-order bands. The results agree nicely with 3D particle-in-cell code simulations. Practical implications of the findings are discussed.