Basics and recent advances in multipactor physics and mitigation*

Multipactor is a nonlinear phenomenon that occurs when electrons driven by a radio frequency (rf) electric field in a high vacuum environment create an avalanche by impacting one or more metallic or dielectric surfaces. The electron avalanche sustains itself by a rapid charge growth through secondary electron emission from the surfaces and can cause a multitude of problems in rf and microwave systems, such as satellite communication payloads and spacecraft components, travelling wave tubes (TWTs), high power microwave sources, and particle accelerators. Mitigation of multipactor has been one of the major challenges for the rf community over the past few decades (A. Iqbal, et al., High Voltage, vol. 8, no. 6, pp. 1095–1114 (2023)).

In this talk, I will first provide a brief overview of basic concepts including secondary electron emission, electron kinetics, multipactor susceptibility, and saturation mechanisms. I will then present recent advances in multipactor mitigation strategies, focusing on engineered device surfaces and engineered non-sinusoidal rf fields (A. Iqbal, et al., J. Vac. Sci. Technol. B 38, 013801 (2020); J. Appl. Phys. 134, 153304 (2023); Phys. Rev. E 102, 043201 (2020)). In addition to vacuum electron multipaction, multipactor‐induced ionization breakdown and its recent advances (D. Wen, et al., Phys. Rev. Lett., 129, 045001 (2022)) are also highlighted.