The electron-cyclotron resonance thruster with magnetic nozzle relies on two successive energy transfer processes: first from electromagnetic energy to electron thermal energy, facilitated by a coupling structure; and second from electron thermal energy to ion directed kinetic energy, facilitated by a diverging magnetic field. The nature and geometry of the coupling structure are crucial to the first energy transfer process. This paper presents an experimental study of the performance of an electron-cyclotron resonance thruster with magnetic nozzle, equipped either with a waveguide-coupling structure or with a coaxial-coupling structure. The necessity of thrust balance measurements to perform such a comparison is demonstrated. The low coupling efficiency from microwave power to the plasma achieved by waveguide coupling is found to result in very large uncertainty with respect to the deposited power. A method to significantly reduce this uncertainty is proposed and implemented. Thrust balance measurements indicate $500\mu \mathrm{N}$ for the coaxial-coupled thruster and $240\mu \mathrm{N}$ for the waveguide-coupled thruster, both operated at 25 W of deposited microwave power and a mass flow rate of $98\mu \mathrm{g}/\mathrm{s}$ of xenon. Electrostatic probe measurements reveal that this difference can be explained by a difference in ion energy. The results emphasize the critical role of the coupling structure, which may have been previously overlooked.

带磁喷嘴的电子回旋共振推进器依赖于两个连续的能量传递过程：首先是通过耦合结构从电磁能到电子热能；其次是从电子热能到离子定向动能，由发散磁场促进。耦合结构的性质和几何形状对第一次能量转移过程至关重要。本文介绍了带有磁喷嘴的电子回旋共振推进器性能的实验研究，该推进器配备有波导耦合结构或同轴耦合结构。证明了进行这种比较的推力平衡测量的必要性。发现通过波导耦合实现的从微波功率到等离子体的低耦合效率导致关于沉积功率的非常大的不确定性。提出并实施了一种显着降低这种不确定性的方法。推力平衡测量表明$500\mu \mathrm{N}$ 对于同轴耦合推进器和 $240\mu \mathrm{N}$ 对于波导耦合推进器，两者都在 25 W 的沉积微波功率和质量流量下运行 $98\mu \mathrm{G}/\mathrm{秒}$氙气。静电探针测量表明，这种差异可以用离子能量的差异来解释。结果强调了耦合结构的关键作用，这在以前可能被忽视了。