Plasma thrusters are required for deep space applications for reducing the fuel payload. This paper evaluates the capability of a Compact ECR Plasma Source (CEPS) as a standalone plasma thruster in space. The unique magnetic field profile of CEPS' ring magnets enables very efficient plasma production and electron heating within the CEPS plasma source section (ID ≈8.5 cm, length ≈11.6 cm) resulting in high plasma potentials. Experiments were undertaken with the CEPS attached coaxially to a larger expansion chamber (ID ≈48.2 cm, length ≈75 cm). Diagnostics included specially designed Langmuir probes (LP) and ion energy analyzers (IEA) that are capable of withstanding the harsh plasma conditions in front of and within the CEPS. LP measurements reveal high-density argon plasma (≈1012 cm-3), with high bulk electron temperatures (≈20 eV) and plasma potentials (≈100 V) at very modest microwave power (≈600 W) over a wide range of pressures (0.3 – 1 mTorr). An important observation is the fall of almost the full plasma potential inside the CEPS within a short distance close to its exit, giving rise to strong ambipolar electric fields suitable for accelerating ions. IEA measurements confirmed the presence of streaming ions with energies ≈87 eV at ≈2 cm in front of the CEPS. Estimates based on the IEA results yield thrust values ≈50 mN at ≈0.5 mTorr. A 2-zone, global model was developed to determine the steady state plasma parameters (including plasma flow velocity) in the geometry of the experimental system (without magnetic field). The model reproduced the key experimental plasma parameters and was extended to compute plasma thrust under actual space-like conditions. The computed thrust values for xenon are higher (≈80 mN) than that for argon (≈40 – 45 mN) at ≈600 W of microwave power.

中文翻译：

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使用 2-Zone 全局模型和等离子体测量对紧凑型 ECR 等离子体源进行推力评估

深空应用需要等离子推进器来减少燃料有效载荷。本文评估了紧凑型 ECR 等离子体源 (CEPS) 作为空间中独立等离子体推进器的能力。CEPS 环形磁铁独特的磁场分布可在 CEPS 等离子体源部分（ID ≈8.5 cm，长度 ≈11.6 cm）内实现非常高效的等离子体生产和电子加热，从而产生高等离子体电位。实验是将 CEPS 同轴连接到更大的膨胀室（ID ≈48.2 cm，长度≈75 cm）。诊断包括专门设计的朗缪尔探针 (LP) 和离子能量分析仪 (IEA)，它们能够承受 CEPS 之前和内部的恶劣等离子体条件。LP 测量显示高密度氩等离子体 (≈1012 cm-3)，具有高体电子温度 (≈20 eV) 和等离子体电位 (≈100 V)，微波功率 (≈600 W)，压力范围广 (0.3 – 1 mTorr)。一个重要的观察结果是，在 CEPS 出口附近的短距离内，CEPS 内部几乎全部等离子体电位下降，从而产生适合加速离子的强双极电场。IEA 测量证实了在 CEPS 前面约 2 cm 处存在能量 ≈87 eV 的流动离子。基于 IEA 结果的估计在 ≈0.5 mTorr 时产生了 ≈50 mN 的推力值。开发了一个 2 区全局模型，以确定实验系统几何结构（无磁场）中的稳态等离子体参数（包括等离子体流速）。该模型再现了关键的实验等离子体参数，并扩展到计算实际类空间条件下的等离子体推力。在 ≈600 W 的微波功率下，氙的计算推力值 (≈80 mN) 高于氩气 (≈40 – 45 mN)。