Using a direct current (DC) glow discharge electrode as a non-invasive impedance probe for measuring electron density

Area of Science:

• Plasma Physics
• Electrical Engineering
• Materials Science

Background:

• Direct current (DC) glow discharges are crucial in various industrial applications.
• Accurate measurement of plasma parameters, like electron density, is essential for process control.
• Traditional methods, such as Langmuir probes, can perturb the plasma, affecting measurements.

Purpose of the Study:

• To develop and validate a non-invasive method for measuring plasma density.
• To utilize the inherent electrical properties of the discharge for diagnostic purposes.
• To compare the accuracy of the novel method with established techniques.

Main Methods:

• A small radio frequency (RF) signal was applied to the anode of a low-pressure DC glow discharge.
• The discharge was modeled as a resonant RLC circuit, analyzing impedance changes with frequency.
• The anode, normally used to sustain the discharge, was repurposed for impedance probing.

Main Results:

• The impedance spectrum of the DC glow discharge exhibited resonances related to plasma parameters.
• The non-invasive impedance probing method successfully extracted electron density.
• Measurements showed good agreement with traditional Langmuir probe techniques across various pressures and voltages.

Conclusions:

• Non-invasive impedance probing is a viable and accurate method for determining plasma density in DC glow discharges.
• This technique offers advantages by avoiding physical probe insertion and potential discharge contamination.
• The RLC circuit model effectively describes the discharge's electrical behavior for diagnostic purposes.