Effects of rf magnetic field on upstream dielectric multipactor

A theoretic model of upstream dielectric multipactor in TEM microwaves, taking both the rf electric field and rf magnetic field into account, is proposed. In this theory, the growth rate of the window multipactor is predicted. The multipactor is approximately independent of the rf frequency, and much more serious than Kishek's model (1998 Phys. Rev. Lett. 80 193) in the regions of weak dc electric fields and strong rf electric fields. Then, an electromagnetic Particle-In-Cell method is carried out to simulate the multipactor in TEM microwaves. Simulation results show a good agreement with the theoretical results. Furthermore, the lower boundary of multipactor is derived analytically, while there is no upper boundary any more. Finally, a gradually transition between Kishek's model and our model is found by examining microwaves of TE modes. It is found that the upper boundary reappears when the rf frequency of TE modes trends to the cutoff frequency of waveguide.