Fabrication Capabilities for Spherical Foam Targets Used in ICF Experiments

This paper reviews the processes developed at General Atomics (GA) in the past several years to fabricate a variety of spherical foam targets at various densities for the inertial confinement fusion (ICF) community. The two most common chemical systems used to produce spherical foam targets have been resorcinol-formaldehyde (R/F) aerogel and divinylbenzene (DVB). Spherical targets have been made in the form of shells and beads with diameters ranging from approximately 0.5 to 4.0 mm, and densities from 100 mg/cc to 250 mg/cc, with typical high yield of intact shells or beads of 90%-95%. Permeation barriers have been developed and deposited on both R/F and DVB shells. We have also made R/F foam shells with higher pore size (0.10-0.50 mum) in order to increase the cryo-fill fraction when these shells are cryogenically layered with D₂. Another spherical target that is currently under development that will also be discussed is silica aerogels shells and beads. Other foam target materials currently under development, such metal doped R/F aerogel beads for extreme ultra violet (EUV) source experiments will also be discussed