Importance of stepwise ionization from the metastable state in electron cyclotron resonance ion thrusters
Importance of stepwise ionization from the metastable state in electron cyclotron resonance ion thrusters
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DOI：
10.1007/s44205-022-00002-1
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Y. Yamashita;R. Tsukizaki;K. Nishiyama
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文献类型：
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作者：
Y. Yamashita;R. Tsukizaki;K. Nishiyama
在电子回旋共振（ECR）推力器中，等离子体模式转换是一个关键现象，因为它决定了最大推力性能。在ECR离子推进器中，电离通常发生在磁约束区，在那里电子被ECR连续加热并被磁镜约束。然而，随着流量的增加，电离也观察到的磁约束区域外，这诱导等离子体模式转变。在我们以前的工作中，双光子吸收激光诱导荧光（TALIF）分析表明，从亚稳态的逐步电离在电离过程中起着重要的作用。然而，由于亚稳态的寿命很长，逐步电离的分布尚未被揭示。在这项研究中，这种分布进行了研究，使用一个实验和两个数值方法。首先，TALIF应用于两种类型的气体喷射，其推力性能和基态中性密度分布具有明显差异。在第一次模拟中，亚稳态粒子模拟被用来估计激发率分布。在第二项研究中，微波电场的模拟被用来估计逐步电离等离子体密度的贡献。实验和数值计算结果表明，由于亚稳粒子的扩散，分步电离扩展到磁约束区之外，这种扩展导致了等离子体模式的转变，从而解释了两种气体注入方式的差异。
In electron cyclotron resonance (ECR) thrusters, the plasma mode transition is a critical phenomenon because it determines the maximum thrust performance. In ECR ion thrusters, ionization generally occurs in the magnetic confinement region, where electrons are continuously heated by ECR and confined by magnetic mirrors. However, as the flow rate increases, ionization is also observed outside the magnetic confinement region, and this induces the plasma mode transition. In our previous work, two-photon absorption laser-induced fluorescence (TALIF) analysis revealed that the stepwise ionization from the metastable state plays an important role in the ionization process. However, the distribution of the stepwise ionization has not yet been revealed because of the long lifetime of the metastable state. In this study, this distribution was investigated using one experimental and two numerical approaches. First, TALIF was applied to two types of gas injection with clear differences in thrust performance and ground-state neutral density distribution. In the first simulation, the metastable state particle simulation was used to estimate the excitation rate distribution. In the second study, simulations of the electric field of microwaves were used to estimate the contribution of the stepwise ionization to the plasma density. The experimental and numerical results revealed that the stepwise ionization spreads outside the magnetic confinement region because of the diffusion of metastable particles, and this spread induces the plasma mode transition, explaining the difference between the two types of gas injection.