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arXiv 2309.00565physics.plasm-phphysics.comp-ph
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磁场曲率对不同推进剂霍尔推力器等离子体放电径向-方位向动力学的影响

Influence of the magnetic field's curvature on the radial-azimuthal dynamics of a Hall thruster plasma discharge with different propellants

Maryam Reza, Farbod Faraji, Aaron Knoll

AI总结:

本文通过高保真降阶PIC模拟,研究了磁场曲率对霍尔推力器径向-方位向等离子体放电的影响,发现正负曲率导致不稳定性类型、等离子体性质及离子束发散存在显著差异。

摘要:

外加磁场的拓扑结构是霍尔推力器设计中的一个重要方面。对于现代霍尔推力器,磁场拓扑通常具有弯曲的磁力线,在磁场峰值上游呈凹形(负)曲率,下游呈凸形(正)曲率。此外,磁屏蔽技术的出现使得霍尔推力器的设计采用了非常规磁场,其峰值上游具有高度的凹曲率。我们对磁场曲率对等离子体性质及底层过程的影响进行了严谨而详细的研究,研究采用代表霍尔推力器径向-方位向截面的二维构型。分析针对三种推进剂的等离子体放电进行:氙、氪和氩。对于每种推进剂,我们进行了高保真降阶粒子网格(PIC)模拟,考虑了不同程度的正、负磁场曲率。同时,针对氙进行了相应的二维径向PIC模拟,以比较一维和二维模拟的观测结果。我们观察到,在正、负场曲率情况下,等离子体现象存在显著差异。正曲率情况下的不稳定性谱主要由电子回旋漂移不稳定性主导,而负曲率情况下则以修正双流不稳定性为主。等离子体性质的分布,特别是电子和离子温度,以及各种机制对电子跨场输运的贡献,随场曲率变化显著,尤其是在正、负曲率之间。最后,观察到磁场曲率对离子束沿径向和方位向坐标的发散有重要影响。

英文摘要:

The topology of the applied magnetic field is an important design aspect of Hall thrusters. For modern Hall thrusters, the field topology most often features curved lines with a concave (negative) curvature upstream of the field peak and a convex (positive) curvature downstream. Additionally, the advent of the magnetic shielding technique has resulted in the design of Hall thrusters with non-conventional magnetic fields that exhibit high degrees of concavity upstream of the field's peak. We carry out a rigorous and detailed study of the effects that the magnetic field's curvature has on the plasma properties and the underlying processes in a 2D configuration representative of a Hall thruster's radial-azimuthal cross-section. The analyses are performed for plasma discharges of three propellants: xenon, krypton, and argon. For each propellant, we have carried out high-fidelity reduced-order particle-in-cell (PIC) simulations with various degrees of positive and negative curvatures of the magnetic field. Corresponding 1D radial PIC simulations were also performed for xenon to compare the observations between 1D and 2D simulations. We observed that there are distinct differences in the plasma phenomena between the cases with positive and negative field curvatures. The instability spectra in the cases of positive curvature is mostly dominated by the Electron Cyclotron Drift Instability, whereas the Modified Two Stream Instability is dominant in the negative-curvature cases. The distribution of the plasma properties, particularly the electron and ion temperatures, and the contribution of various mechanisms to electrons' cross-field transport showed notable variations with the field's curvature, especially between the positive and the negative values. Finally, the magnetic field curvature was observed to majorly influence the ion beam divergence along the radial and azimuthal coordinates.

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