Search

The aim of this work is to study the properties of Ar–O2 microwave driven surfatron plasmas as a function of the Ar/O2 ratio in the gas mixture. The key parameters are the plasma electron density and electron temperature, which are estimated with Thomson scattering (TS) for O2 contents up to 50% of the total gas flow. A sharp drop in the electron density from to approximately is estimated as the O2 content in the gas mixture is increased up to 15%. For percentages of O2 lower than 10%, the electron temperature is estimated to be about 2–3 times higher than in the case of a pure argon discharge in the same conditions ( eV) and gradually decreases as the O2 percentage is raised to 50%. However, for O2 percentages above 30%, the scattering spectra become Raman dominated, resulting in large uncertainties in the estimated electron densities and temperatures. The influence of photo-detached electrons from negative ions caused by the typical TS laser fluences is also likely to contribute to the uncertainty in the measured electron densities for high O2 percentages. Moreover, the detection limit of the system is reached for percentages of O2 higher than 25%. Additionally, both the electron density and temperature of microwave discharges with large Ar/O2 ratios are more sensitive to gas pressure variations. [ABSTRACT FROM AUTHOR]

The vacuum ultraviolet (VUV) radiation emitted by hydrogen surface-wave-driven plasmas operating at microwave frequency (2.45 GHz) and low-pressure conditions (0.1–2 mbar) was investigated, in particular the influence of microwave power and gas pressure on the intensity of the emissions. The strong emission of Lyman H2 and Werner H2 molecular bands in the 80–125 nm spectral range was detected, while the most intense atomic emissions observed correspond to Lyman-α and Lyman-β lines at 121.6 nm and 102.6 nm respectively. An increase of the atomic lines and molecular bands intensities with increasing microwave power at pressure 0.1 mbar was observed. At 2 mbar the VUV spectra are entirely dominated by molecular bands. Theoretical predictions, as obtained from a collisional-radiative model, were validated by the experimental results. [ABSTRACT FROM AUTHOR]