Experimental Study of Fill-Tube Hydrodynamical Effects on Implosions

Abstract

Summary form only given. Planned cryogenic ignition experiments at the National Ignition Facility (NIF) are expected to use a fill tube to introduce liquid DT into the capsule prior to solid layer formation. During the implosion, this fill tube is expected to form a hydrodynamic jet at deceleration that could quench ignition if this jet is sufficiently large and penetrates the core early enough. We have begun the first indirect-drive experiments to explore the hydrodynamic effects of fill tubes on implosion performance. In these experiments, we have concentrated on developing diagnostic techniques by replacing the fill tube with a bump on the outer shell surface. This bump is hydrodynamically similar to a fill tube but much easier to fabricate and simulate. We present experimental data and calculations for various bump diameters and heights obtained from two techniques: emission imaging of Ti-doped shell material that has been swept into the core at times near peak compression, and backlit imaging of the bump at early times