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。烧蚀的金属形成一种由气溶胶（纳米级粒子）和原子蒸汽混合而成的扁平羽状物。它们最终在反应堆腔室的另一侧凝结，但气溶胶的行为不会遵循烧蚀金属的流体动力学描述。为了建立一个研究气溶胶形成的数据基础，我们在玻璃板上沉积了一层10微米厚的铅膜，通过放电加热模拟了这一现象。10微米厚的膜对应于布拉格峰内烧蚀的部分，玻璃板对应于剩余的液态金属。5 × 10 × 0.01 mm的铅膜被储存在电容器中的300J电脉冲加热。烧蚀后的羽流在距膜不同距离的见证板上被捕获。用扫描电子显微镜观察捕获的材料，用x射线激发荧光测厚仪非破坏性地测量更多的pe和平均厚度。在我们的实验中，Pb膜消耗的面能密度与α粒子相似（0.2MJ/m^2），但加热时间比α加热（0.1微秒）长100倍。当膜与见证板之间的距离大于20mm时，我们成功地捕获了见证板上的气溶胶。发现烧蚀羽流的前半部分以连续金属膜的形式沉积在见证板上，羽流的尾液以微粒子的形式沉积在见证板上。气溶胶的平均直径为30微米。当距离小于此值时，由于源和见证板之间的蒸汽的几何约束效应，捕获的气溶胶直径变大。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，羽流的前部有点像过冷蒸汽，当它与见证板碰撞时，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