The Z-20 reliability calculations

The Z-20 is a pulsed power facility designed to test the characteristics of water switches to be used in the ZR project. The facility consists of a Marx generator feeding into a water dielectric intermediate store (IS), the IS discharges through a gas switch into a water dielectric pulsed forming line (PFL), goes through the water switches into a water dielectric flat tri-plate transmission line (t-line) matched to a resistive load. The facility was also used to determine the effects of an abrupt, coaxial to flat plate, T-line transition in the water switch region, and the use of large flat dielectric plates to separate anode and cathode from the coaxial PFL. An extended technique to calculate the probability of failure, of large surface area water systems, was used to estimate the reliability of the Z-20 system. With this technique we integrated the probability of failure, after partitioning the surface in small steps, with the advantage that the "enhanced" regions get automatically included in the calculation. The system has been operating at voltage levels above 4 MV with more than 400 shots accumulated without a single failure in the water region.