Design and Implementation of a Fast-Sweeping Langmuir Probe Diagnostic for DC Arc Jet Environments

TL;DR

This paper introduces a fast-sweeping Langmuir probe system that offers high temporal resolution for plasma diagnostics, validated in a high-enthalpy arc jet environment, enabling detailed transient plasma measurements.

Contribution

The paper presents an open-source, low-cost, fast-sweeping Langmuir probe design capable of capturing rapid plasma fluctuations up to 200 kHz, suitable for extreme conditions.

Findings

Successfully measured time-resolved electron temperature and density.

Demonstrated operation in high-enthalpy arc jet conditions.

Validated the probe's capability for transient plasma diagnostics.

Abstract

Langmuir probe diagnostics are a cornerstone of plasma characterization, providing critical measurements of electron temperature, electron density, and plasma potential. However, conventional swept Langmuir probes and other traditional electrostatic probes often lack the temporal resolution necessary to capture transient plasma behavior in dynamic environments. This paper presents the design and implementation of a fast-sweeping Langmuir probe system that is open-source, low-cost, and adaptable for a wide range of plasma applications. The probe system incorporates voltage sweeping to resolve rapid fluctuations in plasma parameters at a temporal resolution of up to 200 kHz. To validate its performance, the system was implemented in the 30 kW miniature Arc jet Research Chamber (mARC II), a high-enthalpy DC arc jet facility designed for prototype testing and development. Experimental results demonstrate the probe's capability to operate in extreme aerothermal conditions, providing time-resolved electron temperature and density along the flow's radial profile. This work establishes a robust and accessible Langmuir diagnostic solution for researchers studying transient plasma behavior in high-enthalpy environments.