Surface flashover of fiberglass reinforced plastic in vacuum at cryogenic temperature

We have examined two fiberglass reinforced plastic (FRP) materials G-10 and G-11 in vacuum at room temperature and at 90 K and compared the flashover strength with breakdown of the pure vacuum gap for a parallel plane geometry as a function of gap length. The breakdown strength for the bridged vacuum gap is lowered considerably from a pure vacuum gap, where the bridged gap exhibits a cube root dependence on the gap length. Lowering the temperature of FRP has little effect on the surface flashover strength and, if anything, tends to lower the strength slightly. This may be due to electron impact desorption of condensed gases from the dielectric surface during the conditioning process.