Ion heating in a fast-flowing plasma for applying an advanced space propulsion

本研究旨在建立一种利用磁喷嘴有效加热快速流动等离子体中的离子，并将增加的热能转化为流动热能的技术。在等离子体科学和聚变研究中积累的各种技术为变推力推进器的发展提供了帮助，它是先进航天运输系统中的代表之一。我们对快速流动等离子体的离子加热方法和磁喷嘴中的能量转换进行了详细的研究，得到了以下重要的结果：1.利用螺旋型天线有效地激发了m=-1的剪切Alfven波，并在低密度区的快速流动等离子体中观察到了强烈的离子加热。2.观察了离子-离子碰撞效应、多普勒效应和中性气体的影响。这些发现对离子的有效加热是有用的。3.我们在实验上观察到，加热近100 eV的离子的热能通过一个发散的磁喷嘴被转化为流动能。首次证明了可以通过改变离子加热的输入射频功率来控制排气等离子体的流动能量。4.实验证实了离子加速方向在磁喷嘴中产生了电场，并测量了离子速度分布函数。结果表明，等离子体加速不仅与磁喷嘴的能量转换有关，而且与电场的作用有关，实验证明离子加热可以控制等离子体的加速，这是空间推进器的基础技术，阐明了等离子体加速的机理及其控制方法。在这项研究中，我们获得了许多与离子加热和能量转换技术的建立相关的重要知识。

This research aims to establish the technique for heating the ions in a fast-flowing plasma efficiently and for converting the increased thermal energy into flow one by using a magnetic nozzle. Various technologies accumulated in plasma science and fusion researches help the development of the thruster with variable thrust, which is one of the representative in the advanced space transportation systems. We investigated in detail the ion heating method of a fast-flowing plasma and the energy conversion in a magnetic nozzle, and the following important results were obtained.1.Shear Alfven wave of m=-1 was excited efficiently with a helical-type antenna, and strong ion heating was observed in a fast-flowing plasma in the low density region.2.The effect of ion-ion collisions, the Doppler effect and the effect by the neutral gas were observed. These findings were useful for the efficient ion heating.3.We have observed experimentally that the thermal energy of ions heated nearly 100eV was converted to flow energy by passing through a divergent magnetic nozzle. It was demonstrated for the first time that the exhaust plasma flow energy could be controlled by changing an input RF power for the ion heating.4.It was also experimentally confirmed that an electric field was generated in the magnetic nozzle in the direction of the ion acceleration, and the ion velocity distribution function was measured. It was suggested that not only the energy conversion by the magnetic nozzle but also the effect of the electric field were important for the plasma acceleration.As a result, we have shown experimentally that the plasma acceleration could be controlled by the ion heating, which is a fundamental technology for the efficient space thruster, and clarified the plasma acceleration mechanism and its control methods. In this research, we have obtained a lot of important knowledge related to the establishment of the ion heating and the energy conversion technology.