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This study investigates the impact of surface roughness on the surface discharge characteristics of solid insulators under high vacuum conditions, essential for the insulation design of superconducting magnets operated in such environments. Experiments were conducted to analyze the surface discharge properties in relation to the surface roughness of Polyether ether ketone (PEEK), a material commonly used as a solid insulator in superconducting applications, both in atmospheric and high vacuum conditions. Furthermore, additional experiments were carried out on other widely used solid insulators in superconducting applications, namely Monomer Casting (MC) Nylon, Glass Fiber Reinforced Polymer (GFRP), and Teflon, to assess their surface discharge characteristics under high vacuum. The results indicated that the surface discharge behavior of these solid insulators is significantly influenced by their surface roughness under high vacuum conditions. It was observed that an increase in surface roughness led to a decrease in surface discharge values, whereas a decrease in roughness resulted in higher discharge values. This trend is attributed to the variation in the amount of residual charge on the insulator's surface, which is affected by the surface texture. Consequently, for enhanced electrical stability of superconducting magnets in high vacuum, it is crucial to optimize the surface roughness of solid insulators to minimize residual charges and prevent insulation breakdown due to collision ionization.
Park et al. (Thu,) studied this question.