Spectroscopic study of atmospheric pressure 915 MHz microwave plasma at high argon flow rate

In this paper results of optical emission spectroscopic (OES) study of atmospheric pressure microwave 915 MHz argon plasma are presented. The plasma was generated in microwave plasma source (MPS) cavity- resonant type. The aim of research was determination of electron excitation temperature T-exc gas temperature T-g and electron number density n(e). All experimental tests were performed with a gas flow rate of 100 and 200 l/min and absorbed microwave power P-A from 0.25 to 0.9 kW. The emission spectra at the range of 300 - 600 nm were recorded. Boltzmann plot method for argon 5p - 4s and 5d - 4p transition lines allowed to determine T-exc at level of 7000 K. Gas temperature was determined by comparing the measured and simulated spectra using LIFBASE program and by analyzing intensities of two groups of unresolved rotational lines of the OH band. Gas temperature ranged 600 - 800 K. The electron number density was determined using the method based on the Stark broadening of hydrogen H-beta line. The measured n(e) ranged 2 x 10(15) - 3.5 x 10(15) cm(-3), depending on the absorbed microwave power. The described MPS works very stable with various working gases at high flow rates, that makes it an attractive tool for different gas processing.