Experimental and Analytical Studies of Louvered First-Wall Systems for NIF

The first wall of the National Ignition Facility (NIF) target chamber will be a source of contamination for the final optics assemblies (FOA) debris shields. The expected x-ray fluence on NIF can be as high as 2 J/cm² for 20 MJ target yields. This is sufficiently intense to mobilize first wall material and contaminants that have been deposited on the first wall. Since 90% of the aluminum target chamber surface area will consist of first wall panels, it is critical to choose a material that is not easily mobilized by target x-ray emissions. Additionally, it would be advantageous to have a first wall design that provides a sink for mobilized material in the target chamber. With these issues at hand, a louver design has been proposed as the configuration of the NIF first wall. Experiments simulating the proposed louver geometry were fielded on Nova at x-ray fluence levels comparable to those expected on NIF. The results of these experiments were applied to the understanding of NIF contamination issues and used as a benchmark for the TSUNAMI code. Numerical studies were performed to measure the collection efficiency of the louver design where several parameters including louver length, distance between louvers, and x-ray fluence were varied.