In wall-less Hall thrusters, the ionization of the propellant and the acceleration of the ions occur outside the thruster [S. Mazouffre, S. Tsikata, and J. Vaudolon, in 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (American Institute of Aeronautics and Astronautics, Cleveland, OH, 2014)]. This reduces interactions between the plasma and the thruster parts as compared to conventional annular and cylindrical Hall thrusters and promises a longer thruster lifetime. With a much simpler design, these non-conventional thrusters are also easier to miniaturize for operation at low power levels of a few hundred watts and lower. In this work, experiments demonstrate that a miniaturized (3 cm diameter) 200 W wall-less thruster is also able to achieve similar voltage utilization, propellant utilization, and current utilization efficiencies as conventional Hall thrusters. Yet, thruster performance of the wall-less thruster is generally lower due to a much larger plume divergence than that in conventional Hall thrusters. This plume divergence is a consequence of ion acceleration in the fringing magnetic field. Thrust and plasma measurements suggest that the thrust generated by the wall-less thruster is due to two components: ion acceleration by the JxB force in the region of the fringing magnetic field radially away from the thruster and by plasma expansion in the diverging magnetic field near the thruster axis.

中文翻译：

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无壁霍尔推进器中的离子加速

在无壁霍尔推进器中，推进剂的电离和离子的加速发生在推进器的外部 [S. Mazouffre、S. Tsikata 和 J. Vaudolon，在第 50 届 AIAA/ASME/SAE/ASEE 联合推进会议上（美国航空航天研究所，俄亥俄州克利夫兰，2014 年）]。与传统的环形和圆柱形霍尔推进器相比，这减少了等离子体和推进器部件之间的相互作用，并保证了更长的推进器寿命。通过更简单的设计，这些非常规推进器也更容易小型化，以在几百瓦或更低的低功率水平下运行。在这项工作中，实验表明小型化（3 厘米直径）200 W 无壁推进器也能够实现与传统霍尔推进器类似的电压利用率、推进剂利用率和电流利用率。然而，与传统霍尔推进器相比，无壁推进器的推进器性能通常较低，因为羽流发散要大得多。这种羽流发散是边缘磁场中离子加速的结果。推力和等离子体测量表明，无壁推进器产生的推力是由两个组成部分造成的：径向远离推进器的边缘磁场区域中 JxB 力的离子加速和附近发散磁场中的等离子体膨胀推进器轴。