Saravia M M, Giacobbe A, Andreussi T
Department of Civil and Industrial Engineering, University of Pisa, 56122 Pisa, Italy.
Department of Physics, University of Pisa, 56127 Pisa, Italy.
Rev Sci Instrum. 2019 Feb;90(2):023502. doi: 10.1063/1.5079532.
We developed a new experimental approach to characterize the plasma behavior inside Hall thrusters. The main novelty of the developed approach regards the combination of a triple Langmuir probe, which guarantees a high flexibility, and Bayesian data analysis. The triple Langmuir probe was mounted on an articulated arm that can rapidly insert the probe inside the thruster channel, providing a clear picture of relevant plasma properties along the channel centerline, from the near plume to the near-anode region. At a given operating condition of the thruster, multiple measurements were performed, changing the arrangements of the triple probe electrodes and the applied potential differences between the electrodes. Then, in order to analyze the data gathered by the triple probe, a Bayesian integrated data analysis has been adopted. This method made it possible to combine measurements from different electrode arrangements and to improve the quality of the inferred plasma parameters. Non-uniformities of the plasma sensed by the probe electrodes were taken into account within the physical model of particle collection. In order to model the interaction of the electrodes with the plasma, a parametrization of the Laframboise sheath solution was used. The developed diagnostic system, together with the integrated data analysis, proved to be a valid approach to characterize the plasma flow in Hall thrusters, offering not only a good spatial resolution of the electron temperature, plasma density, and space potential but also a consistent estimate of the measurement accuracy.
我们开发了一种新的实验方法来表征霍尔推力器内部的等离子体行为。所开发方法的主要新颖之处在于将具有高灵活性的三朗缪尔探针与贝叶斯数据分析相结合。三朗缪尔探针安装在一个铰接臂上，该铰接臂可以将探针快速插入推力器通道内，从而提供沿通道中心线从近羽流区到近阳极区相关等离子体特性的清晰图像。在推力器的给定运行条件下，进行了多次测量，改变了三探针电极的排列以及电极之间施加的电位差。然后，为了分析三探针收集的数据，采用了贝叶斯集成数据分析。该方法使得能够将来自不同电极排列的测量结果结合起来，并提高推断的等离子体参数的质量。在粒子收集的物理模型中考虑了探针电极感测到的等离子体的不均匀性。为了模拟电极与等离子体的相互作用，使用了拉弗朗布瓦兹鞘层解的参数化方法。所开发的诊断系统与集成数据分析一起，被证明是表征霍尔推力器中等离子体流动的有效方法，不仅能提供电子温度、等离子体密度和空间电位的良好空间分辨率，还能对测量精度进行一致的估计。
