Higher-order, asymmetric orbit multipactors

Multipactors involving asymmetric back-and-forth orbits with different flight times and launch phases are studied. Resonant orbits with the rf involve periodic sequences of two or more different impact phases. Such orbits appear when the rf field and emission velocity reach values that make the usual symmetric orbits unstable, through a stability bifurcation process. The number of resonant impact phases contained in each orbit doubles at each bifurcation, leading to higher-order multipactor. Existence of second- and third-order multipactors is demonstrated, extending the theoretical upper-field boundary for multipactor discharge. The study focuses on orbital properties, without addressing secondary yield in detail.