Vacuum surface flashover is a critical factor limiting the insulation reliability of ion source extraction systems. This study proposes a structural mitigation strategy based on the secondary electron emission avalanche (SEEA) theory. The electric field distribution at the metal–vacuum–dielectric triple junction is analyzed through finite element simulations, revealing strong local field distortion. A grooved plasma electrode design is introduced to suppress the peak electric field in this region. Simulation results confirm that the groove structure significantly reduces electric field intensity, thereby lowering flashover risk. Furthermore, the impact of groove geometry on vacuum conductance is assessed using molecular flow theory, highlighting a coupling constraint between field suppression and gas evacuation. The findings suggest that future designs should comprehensively balance electric field mitigation and vacuum performance.

Vacuum surface flashover, Secondary electron emission avalanche theory, Electric field distribution optimization, Ion source extraction system