The coupling physics between multiple coaxial antennas separated axially along plasma column produced by helicon antenna are investigated. Experiments are carried out on a recently built device, named Physics ANd Thruster oriented HElicon Research (PANTHER) with the upgrade of second-stage antennas. Mutual induction currents on these antennas are measured for two cases: without plasma discharge and with plasma discharge, respectively. It is found that the existence of a plasma column going through these antennas increases the coupling effects among them significantly. Theoretical analyses from the perspectives of transformer and magnetic permeability and moment confirm the reasonability of this phenomenon. Equivalent circuit models and governing equations are provided for preliminary analyses, covering both single-antenna-driven cases and dual-antenna-driven cases. The effects of confining magnetic field and background pressure on the mutual coupling are shown as well. This work is of particular interest for electrodeless plasma source or thruster which employs multiple coaxial antennas for ionization and acceleration. The analogy of a plasma column going through multiple antennas to a magnetic core for a transformer is an innovative attempt.

中文翻译：

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螺旋天线产生的等离子柱周围的多个同轴天线之间的耦合

研究了螺旋天线产生的沿等离子体柱轴向分离的多个同轴天线之间的耦合物理特性。实验是在最近制造的设备上进行的，该设备名为面向物理和推进器的 HElicon Research (PANTHER)，并升级了第二级天线。在两种情况下测量这些天线上的互感电流：分别没有等离子体放电和有等离子体放电。发现通过这些天线的等离子体柱的存在显着增加了它们之间的耦合效应。从变压器和磁导率和力矩的角度进行理论分析，证实了这种现象的合理性。提供等效电路模型和控制方程用于初步分析，涵盖单天线驱动和双天线驱动两种情况。还显示了约束磁场和背景压力对相互耦合的影响。这项工作对于采用多个同轴天线进行电离和加速的无电极等离子体源或推进器特别感兴趣。将穿过多个天线的等离子体柱类比为变压器的磁芯是一种创新尝试。