Investigating the electromagnetic structure of the coax-to-triplate transition for the pulse-compression section of the ZR accelerator

The ZR accelerator is a refurbishment of Sandia´s Z accelerator, allowing for a 50-60% increase in peak current delivered to a Z-pinch load. Contributing to its design, a new water-switch pulse-compression section is being tested experimentally on the Z20 test facility (part of Sandia´s national pulsed power development laboratory), and modeled with accurate-geometry 3-D electromagnetic simulation (QUICKSILVER code), and circuit modeling. Based on information acquired from new optical diagnostics Woodworth, JR et al., (2003), more detailed water switching models have been incorporated into the simulations. The simulations can show how energy is launched into higher-order modes under certain nonideal conditions such as water switch jitter, and also how the jitter itself can occur owing to slight differences in the water switch initiation process. The electromagnetic simulations indicate the departure from pure TEM mode structure Johnson, WA et al., (2003), particularly when the frequency content of the pulse is high with fast water switching. The first results from the new switch model are presented.