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[Display omitted] • An ultraviolet irradiation in vacuum technique enhancing flashover voltage of SIR. • Illustrate the influence of UVIV on the chain structure of SIR. • Establish a relation between crosslinking of SIR and surface trap parameters. • Explain the effects of surface traps on surface charging and flashover. • Clarify the UVIV improved flashover mechanisms from microscopic to macroscopic. In surface science, surface flashover, which poses a severe danger to the safe operation of modern silicone rubber (SIR)-based electrical equipment, is a continuous discharge event that happens when an intense electric field is produced along the gas-solid interface. To improve the flashover performance, the ultraviolet irradiation in vacuum (UVIV) technique is proposed to modify the SIR surface and the DC flashover threshold increases approximately 14.8 % after 6 h UVIV treatment. Then, the influence mechanisms of UVIV are investigated from microscopic molecule modification to macroscopic flashover performance: The UVIV generates high-energy photons to break C H and Si C bonds in SIR chains, and atoms, group, side chains, and free radicals in chains recombine through the thermally dynamic, causing SIR chains to crosslink. The crosslink chain structure enhances the deep trap energy around the Si O Si bond and introduces large amounts of deep traps. The increment in surface deep trap energy and density captures electrons. It establishes a high electrostatic near the cathode barrier that impedes subsequent electron injection, causing surface charge density decreases far away from the cathode. The reduced surface charges restrict the collision ionization in gas, finally increasing the DC surface flashover voltage through UVIV treatment. [ABSTRACT FROM AUTHOR]

The effects of the presence of a native oxide film or surface contamination as well as variations in material density on the total electron yield (TEY) of Ru and B 4 C were assessed in the absence of any surface charging effect. The experimental results were analyzed using semi-empirical Monte Carlo simulations and demonstrated that a native oxide film increased the TEY, and that this effect varied with film thickness. These phenomena were explained based on the effect of the backscattered electrons (BSEs) at the interface between Ru and RuO 2 , as well as the lower potential barrier of RuO 2 . Deviations in the material density from the theoretical values were attributed to the film deposition procedure based on fitting simulated TEY curves to experimental results. In the case of B 4 C, the TEY was enhanced by the presence of a 0.8-nm-thick surface contamination film consisting of oxygenated hydrocarbons. The effect of the low potential barrier of the contamination film was found to be significant, as the density of the B 4 C was much lower than that of the Ru. Comparing the simulation parameters generated in the present work with Joy’s database, it was found that the model and the input parameters used in the simulations were sufficiently accurate. [ABSTRACT FROM AUTHOR]