Argon gas-puff radius optimization for Saturn operating in the long-pulse mode

Argon gas puff experiments using the long pulse mode of Saturn (230-ns rise time) have promise to increase the coupled energy and simplify operations because the voltage is reduced in vacuum and the forward-going energy is higher for the same Marx charge. The issue addressed in this work is to determine if the 12-cm-diameter triple nozzle used in Saturn long-pulse-mode experiments to date provides maximum K-shell yield, or if a different-radius nozzle provides additional radiation. Long-pulse implosions are modeled by starting with measured density distributions from the existing 12-cm-diameter nozzle, and then varying the outer radius in an implosion-energy-conserving self-similar manner to predict the gas-puff diameter that results in the maximum K-shell yield. The snowplow-implosions and multi-zone radiation transport models used in the analysis are benchmarked against detailed measurements from the 12-cm-diameter experiments. These calculations indicate that the maximum K-shell emission is produced with very nearly the existing nozzle radius.