Effects of surface laser treatment on flashover characteristics across alumina ceramics in vacuum

The surface phenomena across a solid insulating material under high electric field in vacuum are closely related to the surface conditions of the material. The CO₂ laser generator is employed to modify the surface condition of alumina ceramics. The density of scratched lines is 10-50 per 5 mm, and based on adjusting the energy output of laser generator, and the depth of scratched lines is 0.05-0.25 mm. The experimental results show that, there are continuous line-like holes on the surface of alumina ceramics due to heat after laser treatment, and their flashover voltages are changed obviously. While proper adjusting the density and depth of scratched lines, the regular surface microscopic pattern can be achieved and the material exhibits a better surface electric strength. According to the scratching technology in this paper, the larger scratching density and the better scratching effect, the higher flashover voltage. When the density is 50 lines per 5 mm and the depth is 0.2 mm, the surface shows a best microscopic structure and is totally covered by uniform and continuous holes, and the flashover voltage reaches up its maximal value. It is considered that, the uniformity of surface microstructure of a material can be used to describe and regulate its flashover performance.