Simulation and Experimental Investigation of Secondary Electron Emission Regulation on Ferrite Medium Using Raised Microstructures

Ferrite is an essential functional material for high-power nonreciprocal microwave components, such as circulators and isolators, and its secondary electron emission (SEE) property is critical for suppressing the multipactor effect under vacuum conditions. In this work, we propose a surface engineering strategy based on periodic raised microstructures to regulate the secondary electron yield (SEY) of ferrite coatings/substrates. A Monte Carlo-based numerical method is developed to calculate the SEY of ferrite with hexagonal and annular microprotrusions of varying heights and geometric parameters. The dependence of SEY on microstructure dimensions is systematically analyzed. Spinel ferrite samples with designed microstructures are fabricated via mechanical processing. For hexagonal column arrays with a height of 1.5 mm, a side length of 0.5 mm, and a pitch of 1.67 mm, the maximum SEY is reduced from 2.4 (smooth surface) to 1.7 while the annular concentric protrusion arrays decrease the maximum SEY to 2.1. Effective suppression is achieved over the entire incident energy range for both microstructural designs. Despite a lower reduction, the annular arrays offer geometrically isotropic electron trapping, which may be advantageous for devices with circular or coaxial cavity geometries where directional dependence of the surface texture is undesirable. The results demonstrate that tailored surface microstructures can significantly mitigate SEE of ferrite, providing a promising route for developing high-performance ferrite coatings toward multipactor suppression in space microwave devices.