A new technique to make low-density, low-atomic-number foam shells was developed for use in cryogenic laser fusion targets. Shells with sphericity > 99% and wall uniformity > 97% were fabricated by a density matched emulsion method using cross-linked copolymerization in the oil phase of the emulsion. The diameter, wall thickness and density of the shells ranged in 100–1500 μm, 10–150 μm, and 90–310 mg/cm3, respectively. Some foam shells exhibited a membrane on the outer surface, which could be used as the protective layer to prevent liquid fuel from boiling off. The foam shell was transparent when it was saturated with liquid deuterium. This enables us to characterize distribution of the liquid fuel in the shell using an optical interference technique.

A system to provide a liquid or solid deuterium shell target with a plastic ablator for laser implosion experiments was developed. The system is capable of filling a plastic capsule with deuterium gas of 11 MPa at room temperature at the firing position in the target chamber. Then, the target is cooled down to a cryogenic temperature to form a uniform liquid or solid fuel layer inside without exposing it to the atmosphere. Details of the system, tensile strength of polystyrene shells at low temperature, and the residual vapor pressure in the central void of the target at the laser irradiation are described.

We have developed a monitoring system for the real-time characterization of cryogenic fuel layer in laser-fusion targets. This system is composed of an imaging interferometer, in addition to a normal target postion monitor with a single optical path. The fabrication process of a solid fuel layer in a plastic spherical shell is observed with this system. Solid fuel layer uniformity is displayed as concentric interference patterns. The distortions of the interference patterns can be interpreted as fuel layer nonuniformities.