Characterization of an Atmospheric-Pressure Argon Plasma Generated by 915 MHz Microwaves Using Optical Emission Spectroscopy

Robert Miotk,Bartosz Hrycak,Mariusz Jasiński,Jerzy Mizeraczyk

doi:10.1155/2017/6359107

Abstract

The paper presents the investigations of an atmospheric-pressure argon plasma generated at 915 MHz microwaves using the optical emission spectroscopy (OES). The 915 MHz microwave plasma was inducted and sustained in a waveguide-supplied coaxial-line-based nozzleless microwave plasma source. The aim of presented investigations was to estimate parameters of the generated plasma, that is, excitation temperature of electrons Texc, temperature of plasma gas Tg, and concentration of electrons ne. Assuming that excited levels of argon atoms are in local thermodynamic equilibrium, Boltzmann method allowed in determining the Texc temperature in the range of 8100–11000 K. The temperature of plasma gas Tg was estimated by comparing the simulated spectra of the OH radical to the measured one in LIFBASE program. The obtained Tg temperature ranged in 1200–2800 K. Using a method based on Stark broadening of the Hβ line, the concentration of electrons ne was determined in the range from 1.4 × 1015 to 1.7 × 1015 cm−3, depending on the power absorbed by the microwave plasma.

Highlights

An optical emission spectroscopy (OES) [13,14,15,16,17] method has been used for diagnosing the microwave argon plasma
The investigations of an atmospheric-pressure argon plasma generated at 915 MHz microwaves using optical emission
In the tested range of the absorbed microwave power PA by the plasma, we observed an increase in the excitation temperature Texc, the gas temperature Tg, and the concentration of electrons ne

Summary

Introduction

The atmospheric-pressure microwave plasma sources (MPSs) found many different physical and technical applications such as decomposition of gaseous pollutants [1,2,3,4], deposition thin layers in nanosensors [5, 6], medicine for bacteria inactivation [7], and production of hydrogen via conversion of hydrocarbons or other hydrogen carriers [8,9,10,11,12]. Since in process of the gas treatment by the plasma, the temperature of plasma gas and concentration of electrons play an important role; the knowledge of these basic parameters is crucial for understanding the chemical kinetics and its optimization. An optical emission spectroscopy (OES) [13,14,15,16,17] method has been used for diagnosing the microwave argon plasma. The plasma was induced by microwaves at a frequency of 915 MHz in waveguide-supplied coaxialline-based nozzleless MPS [1]. The presented device allows the generation of so-called cold plasma which is classified as a partial local thermodynamic equilibrium (PLTE) plasma [13, 14, 18,19,20]

Experiment

Results

Conclusions