Study of physics and practical applications of laser-driven in-tube accelerator

对自行研制的激光驱动管内加速器进行了基础和应用研究。在4米高空垂直发射试验中验证了其工作原理。实验和数值研究了脉冲产生机制，重点研究了激波、膨胀波和激光等离子体之间的相互作用以及伴随的流体动力学不稳定性。建立了其推进性能的标度规律。实验证明了激光烧蚀对脉冲增强的作用。这些在实际应用中很有用。在该装置中，动量耦合系数（定义为脉冲与激光能量之比）可以通过约束效应和适当设置工作气体种类及其填充压力而增加三倍。动量耦合系数与声速的倒数成正比，用氩、氪、氙等三种单原子气体进行了实验验证。还得到了它们的电离势对脉冲的二次效应。脉冲性能的唯一特征是使用无量纲动量耦合系数，即量纲动量耦合系数乘以声速，以及无量纲参数，即填充压力乘以有效弹丸体积与激光能量的比值。实验和数值分析表明，激光等离子体的有效膨胀体积可以优化脉冲性能。在激光烧蚀性能实验中，聚缩醛表现出最好的性能；它的冲量对环境压力很敏感。在适当的激光流量下，脉冲在环境压力低于100pa时达到最高。这种良好的性能不仅可以用于提高装置的推进性能，而且可以用于包括空间碎片脱轨在内的其他各种空间应用。少

Basic and application studies were conducted on the laser-driven, in-tube accelerator which had been developed by the head investigator. The operation principle was experimentally validated in 4-m-high vertical launch experiment. The impulse generation mechanisms were experimentally and numerically studied by highlighting the interactions among shock waves, expansion waves and laser-generated plasma and accompanying fluid-dynamics instabilities. A scaling law of its propulsion performance was established. The impulse enhancement using laser ablation was experimentally demonstrated. Those are useful for practical applications. In this device, the momentum coupling coefficient, which is defined as the ratio of an impulse to a laser energy, can be tripled owing to a confinement effect and with appropriate setting of the working gas species and its fill pressure. The momentum coupling coefficient scales with the reciprocal of the speed of sound, which was experimentally validated using thr … More ee kinds of monoatomic gases, argon, krypton and xenon. The secondary effect of their ionization potential on the impulse was also obtained. The impulse performance is uniquely characterized using a dimensionless momentum coupling coefficient, the dimensional momentum coupling coefficient multiplied by the speed of sound, and a dimensionless parameter, the ratio of the fill pressure multiplied by an effective projectile volume to the laser energy. From the experimental and numerical analysis, it is concluded that the impulse performance can be optimized from the effective expansion volume of the laser plasma. In the laser-ablative performance experiment, polyacetal exhibited the best performance ; its impulse is sensitive to the ambient pressure. At an appropriate laser fluence, the impulse becomes highest at ambient pressures below 100 Pa. This favorable performance can be useful not only for improving the propulsive performance of the device but also for other various space applications including space debris deorbiting. Less