Space Propulsion System using Relativistic Plasma Beams through Intense Laser-Solid Nonlinear Interactions

在实验中，利用测得的速度，比较和阐明了推进剂香气/Re的作用机理。在理论分析中，对相对论粒子的推力性能进行了如下讨论：(1)比较了不同激光条件下的推力性能，测量比较了不同激光和靶面条件下的推力性能，并讨论了最佳条件。(2)通过数值模拟研究了发射机理，开发了一种适用于高功率激光与固体相互作用的1.5维PIC程序。对薄膜靶正向粒子加速进行了数值模拟。此外，还研究了这些粒子的加速机制，包括强电场的产生机制。(3)通过测量靶-等离子体势研究了加速机理，用单探针估计了靶-等离子体势的时间变化，并估计了静电场强度和强度的时间变化。结果表明，目标与等离子体之间的静电场是主要的加速机制。(4)相对论粒子推进性能的理论研究相对论粒子束推进性能。结果表明，当粒子速度接近光速时，在给定输入功率下的推力接近于仅用激光本身产生的推力。此外，相对论条件下的推力几乎与粒子的质量流量无关。这些结果将使旧的光子推进概念复兴为新的“直接激光推进”概念。

In the experiment, using measured velocities, propulsive perfume/re and mechanism were compared and elucidated. In the theoretical analysis, thrust perfermances using relativistic particles were discussed, as follows.(1) Comparison of thrust performances for various laser conditions Propulsive performances for various laser and target conditions were measured and compared, and optimum conditions were discussed.(2) Investigation of arreleration mechanism with numerical simulation A 1.5-D particle-in-cell (PIC) code was developed for high-powerlaser-solid interaction. Forward particle acceleration from a thin film target was simulated. Hi addition, the acceleration mechanism of these particles including that of generation of intense electric field was investigated.(3) Investigation of acceleration mechanism through measurement of target-plasma potential Temporal variations of target-plasma potentials were estimated with single probes, and temporal variations of strengths of electrostatic field and forte were estimated. As the result, the primary acceleration mechanism was found to be the electrostatic field between the target and plasma.(4) Theoretical investigation of propulsive performance using relativistic particles Propulsive performances with the use of relativistic particle beams were investigated. As the result, the thrust at given input power approached that generated only with the laser itself when the velocity of the particles was assumed to be approaching the speed of light It was also shown that thrust at the relativistic condition was almost independent on mass flow rate of the particles. These results will revive the old photon propulsion concept as the novel "direct laser propulsion" concept.