Flux-throttled Radiation Flow in a Foam Tube*

We have established a high energy density campaign to study the robustness of supersonic, diffusive radiation flow in experiments at the National Ignition Facility (NIF). The target package is comprised of a silica foam tube with tantala foam walls, which is exposed to a radiation drive of ~200 eV, created by a laser-driven hohlraum. Heated tantala walls minimize radiation loss from the flow inside silica [1]. We throttle the radiation flux entering the silica tube by using blocking washers of various widths. A measurement of radiation flow breakout then provides an experimental scenario for validating radiation hydrodynamics codes. Here, we present 2D, pre-shot radiation hydrodynamics simulations that have guided the design of upcoming experiments. We show that radiation flow fails to reach breakout once the blocking washer covers 50% of the silica annular width. One shot has been performed for the unblocked setup (N170806-004), and our simulation results compare well with the radiation flow timing and flux measurements in that case.

[1] O. A. Hurricane and J. H. Hammer, Phys. Plasmas 13, 113303 (2006).