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

在未来具有液体第一壁的激光聚变反应堆中，液体壁（LiPb）的表面将被聚变燃烧产生的α粒子烧蚀。烧蚀的金属形成一个平面状的羽流，由气溶胶（纳米尺度的粒子）和原子蒸气组成。它们最终在反应器室的另一侧凝结，但气溶胶的行为不会遵循烧蚀金属的流体动力学描述。为了给讨论气溶胶的形成提供一个数据基础，我们用放电加热沉积在玻璃板上的10微米厚的铅膜来实验模拟这种现象。约10微米厚的膜对应于布拉格峰内的烧蚀部分，玻璃板对应于剩余的液态金属。烧蚀后的羽流被捕获在位于离膜不同距离处的验证板上。用扫描电子显微镜观察捕获的材料 关于我们 PE和平均厚度使用X射线激发荧光厚度计非破坏性地测量。在我们的实验中，Pb膜中消耗的面能量密度与α粒子的面能量密度相似（0.2MJ/m^2），但加热时间比α加热长100倍（0.1微秒）实验结果表明，当薄膜与验证板之间的距离大于20 mm时，我们成功地捕捉到了验证板上的气溶胶。作为连续的金属膜沉积在验证板上，并且羽流的拖尾部分作为微粒沉积在膜上。气溶胶的平均直径为30微米。当距离小于此值时，由于水汽在源和验证板之间的几何约束效应，捕获气溶胶的直径变大。这一结果与基于Luk'yanchuk模型的理论模型一致。我们的模型分析表明，羽流的前部类似于过冷蒸汽，当它与验证板碰撞时会形成连续的膜。少

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