REDISTRIBUTION OF SOLID FUEL LAYER IN LASER FUSION TARGET BY ELECTRODE-LESS DISCHARGE OF MICROWAVE

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Plasma layring technique to make a cryogenic target for a laser fusion reactor has been developed. A 6-mm-diameter quartz shell housed in a microwave cavity was cooled to 10 K to freeze appropriate amount of deuterium inside. A nonuniform solid deuterium layr in the shell was successfully redistributed into uniform one by initiating a glow discharge in the void.1) The time constant for redistribution was 80 second. This time constant is much less than that driven by heat initiated by tritium decays. This short time constant is beneficial for the future laser-fusion reactor-system since it can reduce the tritium inventory in a pellet factory.2) The time constant for redistribution is primary determined by cooling performance of the shell and the time constant has week dependence on the power of the microwave. Reducing the temperature of the cooling helium is most effective to shorten the time constant.3) Solid deuterium, which was initially opaque due to cracks, turned into transparent by heating with the glow discharge. Cracks in the solid were removed toward the heat source through a sublimation / deposition cycle. This is an important result to obtain a high quality solid fuel layr for the laser fusion target.