PBFA II-Z: A 20-MA driver for Z-pinch experiments

Sandia is modifying the PBFA II accelerator into a dual use facility. While maintaining the present ion-beam capability, the authors are developing a long-pulse, high-current operating mode for magnetically-driven implosions. This option, called PBFA II-Z, will require new water transmission lines, a new insulator stack, and new magnetically-insulated transmission lines (MITLs). Each of the existing 36, coaxial water pulse-forming sections will couple to a 4.5-/spl Omega/, bi-plate water-transmission line. The water transmission lines then feed a four-level insulator stack. The insulators are expected to operate at a maximum, spatially-averaged electric field of /spl sim/100 kV/cm. The MITL design is based on the successful biconic Saturn design. The four "disk" feeds will each have a vacuum impedance of -2.0 /spl Omega/. The disk feeds are added in parallel using a double post-hole convolute at a diameter of 15 cm. They predict that the accelerator will deliver 20 MA to a 15 mg Z-pinch load in 100 ns, making PBFA II-Z the most powerful Z-pinch driver in the world providing a pulsed power and load physics scaling testbed for future 40-80 MA drivers.