The first successful fabrication of a cryogenic foam target is reported. Detailed techniques to ensure accurate fuel loading in the foam shell are described. This target has been used for implosion experiments with the Gekko XII glass laser.

Spherical hollow polymer foam shells used as a sustainer of cryogenic fuel for the inertial fusion target have been developed. Foam shells which have 500–1000 μm diameter with a 30–100 μm uniform wall, 4 μm cell size and 40 mg/cm3 density, have been fabricated using a dual-nozzle droplet generator and a freeze-dry technique. Requirements to obtain a uniform thick wall and fine cell size are discussed.

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We have presented a novel in situ method which is simple and sensitive, to measure the micromass of the fuel layer in a cryogenic foam target. In this method, a foam shell is mounted on a flexible polyester fiber 7 μm in diameter and 800 μm in length. The fiber is suspended with a stalk which is mechanically vibrated at any given frequency. The resonant frequency of the elastic vibration of a foam-fiber system is measured before and after fuel loading. The mass of the fuel can be determined from the change in the resonance frequency in the range from submicrograms to submilligrams. The resolution of this system, which is limited by the Q factor of the foam-fiber system, is better than 0.2 μg corresponding to the measurement accuracy of 0.1%.