Recommended Practices for Design and Use of Retarding Potential Analyzers in Electric Propulsion

Retarding potential analyzers (RPAs) are relatively simple and powerful diagnostic tools that are capable of providing ion energy distribution functions within the plume of an electric propulsion thruster. The purpose of this paper is to provide a guide to standardize RPA design, construction, operation, error analysis, and data interpretation for operation within the plasma environment produced by an electric propulsion thruster. Operational environment, correction factors, and error analysis are presented along with time-averaged and time resolved probe operation and data analysis methods. These best practices have been compiled from extensive experience using RPAs for electric propulsion thruster testing and previous publications on the design, use, and analysis of data from RPA probes. Focus in this guide is placed on the use of RPAs in the most common electric propulsion devices, namely Hall effect thrusters, where the plasma is flowing and ions have a rich variety of energy and oscillatory behaviors. The strategies presented in this guide are expected to increase the quality and repeatability of testing data obtained from electric propulsion systems, thereby allowing for improved comparisons between different thrusters and operating environments and improving the fidelity of models for on-orbit predictions.

减速电位分析仪（Retarding Potential Analyzers, RPAs）是一类结构简洁却功能强大的诊断工具，可用于获取电推进推力器羽流内的离子能量分布函数。本文旨在提供一份规范指南，用以规范电推进推力器产生的等离子体环境中RPA的设计、搭建、操作、误差分析与数据解译流程。本文将结合时均与时间分辨探针的操作方法及数据分析手段，对工作环境、校正因子与误差分析展开阐述。本指南中的最佳实践基于大量使用RPA开展电推进推力器测试的实际经验，以及过往关于RPA探针设计、使用与数据分析的相关研究文献汇编而成。本指南重点聚焦于最常见的电推进装置——霍尔推力器中的RPA应用场景，此类装置的等离子体处于流动状态，且离子展现出丰富的能量分布与振荡行为。本指南提出的操作策略，有望提升电推进系统测试数据的质量与可重复性，进而推动不同推力器与工作环境间的对比研究，并提高在轨预测模型的保真度。