The National Ignition Facility (NIF) will support multiple user groups who will use NIF's unique capability to generate intense pulses of x-ray, neutron and gamma radiation from non-ignition and ignition targets. The NIF baseline design includes several features to support these experiments, in particular for large experiment packages that can be introduced through two large ports located at the chamber waist and bottom. Some of these experimental packages will require target-facing surfaces that almost completely enclose the target. Due to the short stand-off distances of these surfaces, of necessity x-ray ablation inside these confined spaces will generate conditions in NIF quite similar to those envisioned for future Inertial Fusion Energy (IFE) target chambers like HYLIFE. The design of these NIF experiments provides an excellent opportunity to apply the analytical tools the IFE research community has created, and in a synergistic way, these experiments will in turn provide a rich source of experimental data for IFE target-chamber research.

This paper summarizes the key design issues and phenomena must be understood and modeled to design target-chamber systems with significant target-facing surface areas close to NIF targets. The key phenomena, when the x-ray energy fluences delivered to the target-facing surfaces exceed tens of joules per square centimeter and approach thousands of joules per square centimeter, include ablation of cryogenic and room-temperature materials, surface response, phase change, compressible gas-dynamics, real gas and chemical kinetics effects, radiation transport, venting, structural loading, structural dynamic response, and vapor and debris condensation. The near-term motivation for studying these phenomena is three-fold: for augmenting the National Ignition Facility (NIF) target-chamber performance, the potential exists to enhance the target-chamber protection and debris mitigation using a frost-coated mini-chamber; for placing large experiment packages in the NIF chamber to support stockpile-stewardship and other research efforts, methods must be developed to deal with ablation debris and other technical issues; and for inertial fusion energy (IFE), these issues must be understood to design more compact liquid-protected chambers with the potential to reduce cost and allow more rapid vacuum restoration and higher shot repetition rates.

The technical issues discussed here, or subsets of these issues, should be of interest to several NIF user groups, including those interested in reducing shot intervals from eight to four hours to permit a 1200 shot-per-year NIF schedule, those interested in high-mass or "dirty" targets, those interested in fielding large stockpile-stewardship experiment packages inside the NIF target chamber, those interested in advanced chamber protection concepts for the first heavy-ion ignition facility that will follow NIF, and those interested in studying fundamental chamber clearing phenomena for IFE applications.