In this study, the electrical and optical properties and plasma's parameters of capacitive radio frequency (RF) discharge for the argon and hydrogen mixture at low pressure are investigated using optical emission spectroscopy (OES) and a Langmuir probe. The wavelengths of spectral lines obtained from OES are between 400 and 950 nm. By using the spectral lines and probe data, the electron temperature for every different RF power, mixture rate and flow rate are determined by the modified Boltzmann curve method. The Langmuir probe gives the electron temperature and other plasma properties for the same discharge parameters.

Optical and electrical properties of capacitive coupled radio frequency Ar-H-2 mixture discharge at the low pressure

Optical emission spectroscopy and Langmuir Probe diagnostics were incorporated into the experiment, in which dust particles were formed in-situ by using reactive mixture gases (SiH4/C2H4/Ar) in a radio-frequency (RF) discharge plasma. The excitation temperature was first calculated by combining several optical emission spectra of argon lines and using a Boltzmann distribution to fit the experimental data, then the excitation temperature as functions of both gas pressure and RF power in SiH4/C2H4/Ar discharges for different discharge conditions were obtained. Correspondingly, based on the measurement of the electron temperature by a Langmuir probe, the excitation temperature was compared with the electron temperature, and some discussions were presented. Finally the emission intensities of spectral lines of Si 390.6 nm, Si2+ 380.6 nm and C+ 426.7 nm were measured and presented as functions of pressure, RF power and flow rate of SiH4/C2H4.

http://iopscience.iop.org/article/10.1088/1009-0630/13/5/10/pdf

Diagnostics of Parameters by Optical Emission Spectroscopy and Langmuir Probe in Mixtures (SiH4/C2H4/Ar) Radio-Frequency Discharge

Diagnostic techniques have recently been developed that permit the determination of the deviation from local thermal equilibrium (LTE) in subatmospheric electric arcs and plasma jets. A review is presented of the methods that are applicable to MPD (magnetoplasmadynamic) and arcjet thruster plasmas but that have not been used in space propulsion research. Appropriate plasma diagnostics can lead to increased thrust, better nozzle design, and improved modeling capabilities. These methods include nonintrusive techniques, and can determine the electron, Te, gas, Tg, and total excitation, Texa< temperatures, as well as the electron and atom densities, without using LTE or partial LTE assumptions. General relations for analysis and experimental results for argon constricted arcs, an arc in a rotating magnetic field, and plasma torch jets are presented. The methods discussed can also be applied to plasma mixtures.

T. L. Eddy

Papers

Low-Pressure Plasma Spectroscopic Diagnostics

Low-pressure plasma spectroscopic diagnostics