Multi-harmonic analysis in a floating harmonic probe method for diagnostics of electron energy and ion density in low-temperature plasmas

A floating harmonic probe (FHP) is used to measure the electron energy and ion density in plasmas. It applies an AC voltage to an electrically floated probe and measures harmonic frequency components in the probe current which contains information about the parameters. In this study, we have quantitatively investigated the effects of stray impedances in an FHP measurement system on the calculated parameters. We also discuss the influence of the electron energy distribution function (EEDF) when it deviates from a Maxwellian shape on the FHP measurement. A new approach of multi-harmonic analysis of FHP data (MHA-FHP) is proposed to analyze the electron energy in plasmas with non-Maxwellian EEDFs. The MHA-FHP method has been compared with the conventional FHP and Langmuir probe methods through the measurement of low-temperature argon plasmas. Experimental results indicated that the MHA-FHP method can provide the shape of the EEDFs, effective electron temperature, and ion density.