Lifetime investigation of vacuum surface flashover switch

Vacuum surface flashover switches based on polymers of polyimide (PI), polymethyl methacrylate (PMMA), and monomer cast Nylon as well as fused quartz are respectively designed and tested under condition of charge time 30 μs. The experimental results show that the PI switches are of the highest breakdown voltage and lifetime among the three types of polymers. For breakdown voltage of 416 kV, which is double of that of Nylon, the lifetime of PI switch reaches 750 discharges. The switch resistance of the three types of polymer switches collapses to an order of several ohms within 3 ns, which leads to the rise time of the output pulses in a nanosecond time scale. The breakdown voltage of quartz switches is similar to that of Nylon, which is about 200 kV, and the lifetime is larger than 10 k with conduction current of 2.2 kA. Higher breakdown voltage of quartz specimens is obtained in a shape of a truncated cone, whereas the lifetime gets shorter.