Recommended Practice for Use of Faraday Probes in Electric Propulsion Testing

TLDR

Faraday probes are a common plasma diagnostic used to determine the local ion charge flux of electric propulsion plumes. The paper proposes standard practices, guidelines, and recommendations for experimental methods and analysis techniques to standardize community practices, mitigate test‑environment effects, and reduce systematic measurement error, thereby improving plume predictions in space. The recommended approaches apply to time‑averaged plasma properties in the near‑ and far‑field of electric propulsion plumes, focusing on Hall effect and gridded ion thrusters while also addressing electrosprays, arcjets, and electromagnetic thruster concepts. These test strategies are expected to enhance the quality of comparisons between thrusters and vacuum environments, broaden the applicability of ground‑based measurements, and improve the fidelity of on‑orbit predictions and modeling validation.

Abstract

Faraday probes are a common plasma diagnostic used to determine the local ion charge flux of electric propulsion plumes. Standard practices, guidelines, and recommendations are provided for experimental methods and analysis techniques that aim to standardize community practices, to mitigate test environment effects, and to reduce systematic measurement error in order to improve plume predictions in the space environment. The approaches are applicable to time-averaged plasma properties in the near-field and far-field of electric propulsion plumes, with emphasis on Hall effect thrusters and gridded ion thrusters. Considerations for other electric propulsion technologies are provided, including electrosprays, arcjets, and electromagnetic thruster concepts. These test strategies are expected to increase the quality of comparisons between different thrusters and vacuum environments, thereby broadening the applicability of ground-based measurements and enhancing the fidelity for on-orbit predictions and modeling validation.