Control of charge on insulating glass in vacuum by plasma processing

In order to control the charging of insulating glass used in HV vacuum equipment, the effect of H₂ plasma processing on the glass surface was studied. The electron-beam irradiation method was used to verify the effectiveness of the charging control. Borosilicate glass plates were used as test samples. When the glass was exposed to H₂ plasma produced by ac (60 Hz) voltage application, the surface resistivity of the glass was decreased, varying with H₂ plasma processing time. By exposure to H₂ plasma for 20 min, the surface resistivity was reduced from ∼10¹⁷ to ∼10¹² Ω. Due to the reduction of the surface resistivity, charging of the glass can be controlled to a level below that which could cause surface flashover.