Validation of Hall2De simulations with anomalous ion heating in the pole region of a magnetically shielded Hall thruster

Magnetic shielding in Hall thrusters has been shown to protect the discharge channel walls from ion sputtering thereby eliminating this process as a failure mode. Some low yet measurable erosion has been observed however on surfaces along the side of such thrusters facing the near-plume plasma. With measured rates below 100 μm/kh, NASA’s Hall Effect Rocket with Magnetic Shielding (HERMeS) has featured a low sputtering yield cover of a few millimeters in thickness to protect the front magnetic poles from erosion. In recent work, we argued that anomalous ion heating due to lower hybrid instabilities can play a major role in the erosion of these surfaces. We implement in the 2-D axisymmetric code Hall2De a phenomenological model that accounts for these anomalous effects in the plume region of the thruster. We extract ion velocity distribution functions from the simulations and compare them with those measured by laser-induced fluorescence, showing that the model significantly improves the agreement between the two in the vicinity of the poles. We also show that the simulations predict the measured erosion rates during wear tests within the uncertainty of the measurements. We finally apply the model without modifications to multiple operating conditions, maintaining similar levels of agreement with the experimental measurements.

磁屏蔽在霍尔推力器中的应用已被证实可有效保护放电通道壁免受离子溅射侵蚀，从而将该过程从推力器的失效模式中剔除。不过，在这类推力器朝向近羽流等离子体的侧面表面上，仍观测到了程度较轻但可被定量测量的侵蚀现象。美国国家航空航天局（NASA）的带磁屏蔽霍尔效应火箭（Hall Effect Rocket with Magnetic Shielding, HERMeS）的实测侵蚀速率低于100 μm/kh，其采用了厚度为数毫米的低溅射产额涂层，以保护前磁极免受侵蚀。在近期的研究工作中，我们提出由低混杂不稳定性引发的反常离子加热，会对这类表面的侵蚀过程起到关键作用。我们在二维轴对称仿真代码Hall2De中嵌入了一款现象学模型，该模型可在推力器羽流区中复现上述反常物理效应。我们从仿真结果中提取离子速度分布函数，并将其与激光诱导荧光的实测结果进行对比，结果表明该模型可显著提升磁极附近区域内仿真与实测数据的一致性。此外，我们还验证了该仿真可在测量不确定度范围内，准确预测磨损试验中测得的侵蚀速率。最后，我们未做任何修改，将该模型直接应用于多种运行工况，其与实验测量结果的吻合度仍维持在相近水平。

搜集汇总

背景与挑战

背景概述

该数据集通过Hall2De模拟验证了磁屏蔽霍尔推进器极区异常离子加热现象，并展示了模型预测与实验测量结果的良好一致性，特别是在侵蚀速率预测方面。