Polyimide films featuring surface micron-scale pores for superior multipactor inhibition

In vacuum-dielectric insulation systems, the interface where dielectric is in contact with vacuum is a weak point of insulation, and the frequent occurrence of surface flashover poses a threat to the safe operation of the system. This study proposes a novel approach to mitigate flashover by constructing micron-scale pores on polyimide (PI) surfaces, fabricating films with surface pore diameters of 3.8 ± 0.9 μm, 6.0 ± 1.3 μm, 9.8 ± 2.8 μm, and 11.0 ± 3.6 μm. Experimental results demonstrate PI films with surface micron pores exhibit significantly improved flashover thresholds and a notable reduction in secondary electron yield (SEY). When the pore diameter is 11.0 ± 3.6 μm, the DC and impulse flashover thresholds increase by up to ∼79% and ∼187%, respectively, while the maximum SEY (δ_max) decreases to 1.32. Particle-in-cell (PIC) simulations further validate the inhibitory effect on multipactor. It is observed that electrons are guided into pores during movement and ultimately trapped, significantly slowing down the electron avalanche development, reducing the rate of increase in average surface charge density. The electric field configuration within the pores and pore geometry facilitates the capture of electrons. This study provides an in-depth understanding of the mechanism by which surface micron-scale pores suppress multipactor and alleviate flashover, offering valuable guidance for addressing flashover problems.