Low-Density Materials for Use in Inertial Fusion Targets

Low-density polymer foams have been an integral part of targets used in inertial confinement fusion (ICF) experiments. Target designs are unique in the ICF program, and targets are made on an individual basis. Costs for these targets are high due to the time required to machine, assemble, and characterize each target. To produce targets in high volume and at low cost, a polymer system is required that is amenable to scale up. High internal phase emulsion (HIPE) polystyrene is a robust system that offers great flexibility in terms of tailoring the density and incorporating metal dopants. Emulsions used to fabricate HIPE foams currently are made in a batch process. With the use of metering pumps for both the water and oil phases, emulsions can be produced in a continuous process. This not only makes these foams potential candidates for direct-drive capsules, but high-Z dopants can be metered in making these foams attractive for hohlraum components in indirect-drive systems. Preparation of HIPE foams are discussed for both direct-drive and indirect-drive systems.