Research of aerosol formation of liquid wall laser fusion reactor by electrical discharge method

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In a future laser fusion reactor with a liquid first wall, the surface of the liquid wall (LiPb) will be ablated with alpha particles from fusion burns. Ablated metal make a planer plume that concicts of aerosols (nano-scale particles) and atomic vapor. They finally condense on the other side of the reactor chamber but behavior of the aerosols would not follow hydrodynamic description of ablated metal. To make a data base to discus formation of the aerosols, we experimentally simulated this phenomena using discharge heating of a 10-mcrometer-thick, Pb membrane deposited on a glass plate. The-10-micrometer-thick membrane coresponds to the ablated portion within Bragg peak and the glass plate corresponds to the remaining liquid metal.The 5 x 10 x 0.01 mm Pb membrane was heated by a 300J electric pulse stored in a capacitor. The ablated plume was captured on a witness plate located at different distance from the membrane. Captured materials were observed using a scanning electron microsco … More pe and the average thickness was measured nondestructively using an x-ray stimulated fluorescent thickness meter. In our experiment, the areal energy density consumed in the Pb membrane was similar to that of alpha particle (0.2MJ/m^2) but the heating time was 100 times longer that that by alpha heating (0.1 micro second).We successfully captured the aerosols on the witness plate when the distance between the membrane and the witness plate is more than 20 mm. We found that leading portion of ablated plume deposited on the witness plate as a continuous metal membrane and trailing potion of the plume deposited as micro-particles on the membrane. The average diameter of aerosols was 30 micrometer. If the distance was less than this value, the diameter of captured aerosols became larger due to geometrical confinement effect of vapor between the source and the witness plate. This result agrees with a theoretical model based on the Luk'yanchuk's model. Our model analysis said that the leading portion of the plume is something like a super-cooled vapor, which makes continuous membrane when it collide with the witness plate. Less